What would cause weak ejection on an older pre decocker pt92?
The cases hit me in the face and land on my head.
They land directly behind my feet mostly
i've even had a couple stovepipes because the case didn't kick out fast enough.

Maybe a marriage counselor?  Oh, wait you said ejection. Got confused for a second. Try a different recoil spring.

I wondered about that but wouldn't a weak spring cause the slide to mode too fast resulting in harder ejection?

A bit weaker spring perhaps.

If the extractor spring is weak the brass isn't kicked as hard by the ejector with the case held loosely next to breach face.   I can't remember the design on the ejector on the PT - 92 but if the shape of the ejector is worn it can change how the brass casing is ejected.   One way to tell if it is ammo related is to fire some hot +P ammo, if you still have poor ejection there is probably an issue with the pistol.

The PT-92 is basically a copy of the Beretta 92 which is basically a European design.  Most European designs are made to function with the hotter standard 9 MM loaded in Europe, basically loaded like 123 grain Nato around 1150 FPS.  A lot of US 9 MM are 115 grain with a velocity of 1050 -1100 FPS or 123 grain at 1050-1100 FPS.

Here is a link to Geco Ammunition, notice the 123 grain has a velocity of 1181 FPS and the 115 grain FMJ is over 1200 FPS.  SAAMI tended to spec lower pressure 9's in the US because of a lot of WWIi Lugers and P-38 pistols.  These pistols are pretty much collectors and not shooters today and I wish SAAMI would update their specifications on 9 MM for more modern pistols.

http://geco-munition.de/products/handgun-ammunition.html#!95/0/350

Do the extractor test. Take the slide off of the frame, remove bbl, then slip a live round against the breach until it is grabbed by the extractor. Then turn the slide right side up, like you're going to aim it. The round should not fall out. If it does, you need to tune/replace it.