One fellow said that his dad had cut out the poly bolt rails and installed aluminum. This sounds like a good idea to keep that ejection cycle the same for every cycle of the bolt. I might also make an adjustable (height and width) mag catch to get another point of adjustment.
That would be me.
As I recall, the problem with the Tec 22 my Dad had was that it was very sensitive to magazine position. If you'd push forward on the mag, it would feed round after round after round with no troubles. If you pulled it rearwards, it would jam every few rounds. He used shim stock cut to size and epoxied in place, to change the angle of the mag well. It damned near eliminated magazine related failures.
The bitched-up action rails inside the receiver weren't the cause of the trouble, but they didn't help any. We milled them out, machined new rails (out of steel, according to my Dad) and mounted them by drilling through the receiver from the outside every half inch and securing them using 2-56 machine screws. That really smoothed things up, but we still had intermittent failure-to-fire malfunctions. After looking at it, we noticed that some primers weren't struck as hard as others. Since we shot bulk ammo out of it almost exclusively, variations in rim thickness were almost a definite contributor to the light strike failures.
We replaced the hammer spring, firing pin rebound spring, extractor (VQ unit was installed) and made a firing pin that was .015" longer in the striking area. Fifteen-thousandths of an inch is half of the thickness of a credit card, and the longer firing pin and stiffer hammer spring did away with the light strike problem.
After that, the only problems we had were ammo related. Occasional fail-to-fires, fail to feeds if it got too dirty (to clean it we'd just open it up, hose it with carb/brake cleaner, blow it out with the air compressor, and spray some WD or 3-in-1 in it) and the occasional light-loaded round. Some just plain wouldn't go off, whether they were in my Marlin or in the Tec22.
I had kicked around making a folding wire stock for it (I know, illegal without the stamp, whatev) and figuring a way to mount a cheapo red dot to it, but Pops ended up trading it for a M91/30.