@flying-tiger
I'm back, ☺

according to my xOrganizer I have the v 1.8 version of the arrow, and version v1.9 is out now. I found this on the Just Flight website: https://support.justflight.com/support/solutions/articles/17000068631-pa-28r-turbo-arrow-iii-iv-xp11-changelog
At the bottom of the page I found this:
To download updates you will need to re-download the product from the 'Your Orders' section of your account which you can log into by clicking here.

But my Arrow isn't in "My Orders" of my account because I bought my arrow elswhere.

I re-downloaded en re-installed my Arrow already months ago but that didn't solve the problem at the time. Just to let you know.

Best Regards,
Eddy

@skeptikantin Excellent... I'm very happy you were able to resolve the problem!

@papajoeb Happy you got it working.

@fiene2019flight It's an SU5 bug. I expect it's on the 'to-do' list!

@RFpilot Are you leaning the mixture at higher altitudes? At high altitudes, the mixture needs to be leaned (by pulling the red lever back) because there is less air up there. The engine will lose power if it's not leaned properly. Generally you want to aim for peak EGT (look at the EGT gauge near the throttle levers) for best economy or peak EGT + 100 degrees F for best power.

Sorry, I see the problem now -- I purchased the PA-28R Arrow III & Turbo Arrow III/IV Bundle, for which they are only showing:
COMPATIBILITY FSX/FSX:SE/P3D v1-v4
CURRENT VERSION 2.01
https://www.pcaviator.com/store/product.php?productid=21356&cat=0&page=1

On the other hand, they are showing the PA-28R Turbo Arrow III/IV title as:
COMPATIBILITY FSX/FSX:SE/P3D v1-v5
CURRENT VERSION 2.03
https://www.pcaviator.com/store/product.php?productid=21355&cat=0&page=1

So far their download file has not been updated for the bundle.