Cost index set to 80
VNAV page shows, .80 mach

Upon Leveling off at FL340 speed holds for about a minute, A/T commands .84 to overspeed.

Speed set in the FMC VNAV page to 0.77 M and system holding .8 to 0.81.  MCP setings still have to be set to about 0.04 mach below what you actually want the plane to be at.
P3D v4.5+HF
Active Sky wx
Environment force
Swift client

I understand that in real life the speed is not held perfectly but to overspeed at a cost index of 80 seems off to say the least.

Speed seems to hold better on descent, but not without constant speed brake deployment.

What I would like to try is a complete (by complete I mean COMPLETE) uninstall of 1.4 and start over.  What registry entries need to be blown out to do this? What folders outside of P3D Simobjects and Captain Sim folders should I delete?

I would suggest try using a lower cost index.
Try 60 - I don't know of any airline (not that I know them all!!)that uses such a high CI. Some even use them as low as 25 and 30.
Give it a try.

The cost index setting is not the point.  Regardless of what the cost index is set at, the commanded FMC speed is not being held by the A/T system.  I set a c/i of 30.  The fmc said the cruis speed would be .78 and the A/T system kept the plane at a .82 +/- .02 mach.  I can set the cost index to 1 and the A/T sytem will not keep whatever the calculated cruise speed is.

In other words, no matter where the speed is managed from, the MCP, the C/I figure, the VNAV cruise speed entry...no matter how the speed is set, the A/T system is not keeping that speed with any degree of certainty or accuracy.

As to what airlines fly what cost indices, 80 is very normal according to this site, though I have zero info on the reliabilty of their sources.  80 seems to come up on most sites for American Airlines...
https://costindex-index.fandom.com/wiki/American_Airlines_Cost_Index
https://www.scribd.com/document/374519450/Cost-Index-Database-2017

Here is what I am talking about
First two pics C/I 80 FMC commanding .80 Mach A/T holding 0.82+
Second two pics C/I 30 FMC commanding .78 Mach A/T holding .80+
Last pic, MCP set to SPD mode commanding .80 Mach A/T accelerating past .82...

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So you see it is not a C/I or MCP SPD setting issue.

https://www.captainsim.org/forum/csf.pl?num=1533652095

Captain Sim wrote on Jun 3^rd, 2019 at 3:42pm:

https://www.captainsim.org/forum/csf.pl?num=1533652095

That has nothing to do with managed speed.

You want to me to quote the manual?  Ok, the manual says that when you press a button to do something, then the plane will do what the button pressed said it would.  That is said on about EVERY page of the manual. 

Plus...what I really want is a complete uninstall.

Captain Sim wrote on Jun 3^rd, 2019 at 3:42pm:

https://www.captainsim.org/forum/csf.pl?num=1533652095

It would be a lot more helpful if you mentioned what he's missing -- we're all just trying to get it to work properly.

That being said, it's probably item #6 (upload and attach the flight files).

Mission.Control wrote on Jun 3^rd, 2019 at 7:02pm:

Captain Sim wrote on Jun 3rd, 2019 at 3:42pm: https://www.captainsim.org/forum/csf.pl?num=1533652095 It would be a lot more helpful if you mentioned what he's missing -- we're all just trying to get it to work properly. That being said, it's probably item #6 (upload and attach the flight files).

There is no need to attach flight files.  It happens at every place, every altitude, every speed, every c/i.

There is no need to "quote the manual"  Unless CS wants me to believe that the manual says "cruise speeds will be maintained 0.4+mach above commanded speeds".   If CS does not know what the behavior is supposed to be, that would make the issue understandable.  CS had crappy customer service with the releae of their original 727, which I was one of the first to purchase.  In fact, it too me screaming at CS on email to get the major install/activation issues acknowledged.  The only other shop with this type of customer support arrogance is FSDT. 

Speed is not being managed as indicated in the manuals in any mode.  Speed is not being managed as it would be on the real aircraft.  What good does it do that I can open the cowlings on the engines but will end up on the barber pole or overspeeding at cruise.  On what aircraft do you have to set a C/I of 30 to get the performance of C/I=80?  On what aircraft do you have to set an MCP SPD of .75 to maintain .80? 

I work in customer servic and the addage that the customer is always right is completely wrong.  However, I posted PICTURES of the issue....PICTURES..in different modes of flight and at different times.  I can continue to take pictures, they will all show the same result.

Now, CS, you can tell me to f' off and I will because at the end of the day, I could care less about the money I spent.  I would have been completely happy just to hear "we know about this issue and are working on it".  So here is the deal.  If you want to acknowledge the issue, great.  Work on it.  I didn't need it fixed today.  If you don't want to look into it don't.  Don't tell me about you "system" for bug reporting and other things, when you have not been able to address most of them.  In other words you system, like the managed speed, is not working.

If there is anything CONSTRUCTIVE i can do to track this down, let me know. 

Captain Sim wrote on Jun 3^rd, 2019 at 3:42pm:

https://www.captainsim.org/forum/csf.pl?num=1533652095

This is ridiculous. Who is your QA guy or BETA test pilot? 

Did he ever actully flew this thing ?

ARE YOU ASKING YOUR CUSTOMER TO BE A BETA TESTER FOR YOUR PRODUCT ???