My car (1985.5) has the subtle drop in power like you mentioned. It happens between 3700-3900rpms consistently. I did move my AFM wiper arm at one point but that didn't make a difference. So I'll be curious if you come up with a remedy for yours.

I think I remember reading somewhere that if the idle is set too high, the ICV takes over to bring it back down to around 1K which would cause problems with a poor idle.

I just had some problems with the injection system on mine that ended up being a loose ground connection on the block.

***SOLD***
I have a 1985.5 944NA manual for sale in Unionville, MI.
Just went through the engine a year ago replacing gaskets, seals, vacuum lines, timing and balance shaft belts. Clutch was in good shape when i put engine back in. Has 3,500 miles since then. Could use some paint as well as dash and ...

Speed and reference sensors. Check the section under installation for how to determine which one plugs in where.

https://www.clarks-garage.com/shop-manual/ign-02.htm

A few pictures...

I've got 2 front sets of GAZ GHA515 coilovers and one set of rear shocks for 944 with 18mm mount width. They don't fit my car which has a 20mm width for some reason so the previous owner took a grinder to on of the tabs in an attempt to make them fit. It should be fine to mount since there is plenty ...

So I checked my manifolds and sure enough, the 1-4 was cracked at the Y. Didn't even have to peel of the heat shields as it looks to be cracked all the way around. Got a better condition set on the way.

Good to know. Last summer, while retrieving a 6mm combination wrench that had fallen into the clutch inspection hole in the bellhousing (what are the odds?), I replaced the rear main seal with the National brand one. It might have been leaking a smidge as well but I wouldn't have been able to tell ...

I got the head gasket installed yesterday, oil pan gasket and rear main seal are done already. I bought the Victor Reinz gasket kits for both top and bottom end with the intention of replacing every supplied gasket and o-ring from those kits. There wasn't anything mechanically wrong with the motor ...

Thanks guys! That was my suspicion but I didn't want to create more problems than I was trying to solve. With the way all the other gaskets have been falling apart and o-rings disintegrating I figured the head gasket condition would be the same.