Hello everyone. So I bought an evo fe about 5 months ago and have had a few problems with the tranny. First off the previous owner had the full ets upgrades new act clutch, ets turbo back exhaust, Turbonetics 3 way boost controller, 1300cc injectors with 450 fuel pump.. she's pushing 400whp on e85. I noticed that 4th gear would occasionally pop out and send the rpms high enough to scare the **** out of you. It threw 3rd our maybe once or twice So I researched it could be possible linkage issue. Bought the torque solutions kit with the short throw and replaced all the bushings except the main gate selector bushing (thought torque solutions kit would supply with all other bushings but was terribly mistaken). while installing all that I also used the redline cocktail from MAP. The transmission fluid that was in it could've maybe filled up a shot glass. It was black as oil and the sludgey material on the plug was at least a half inch thick........ after re filling she shifts much smother but 4 will still kick out if you get her past 5k or give to much throttle at all. If you hold the living **** out of the shifter she doesn't kick out. Also when installing the short throw I noticed the little square plastic piece with the rubber gasket that holds the shifter rod down on the cage had a massive Crack in it and I could've probably snapped it into if I tried. Just wondering what my options here are. Transmission f***ked?(highly possible) Something simple?(doubt it) synchros maybe($$) please someone help me out here I'm ready to have this beauty top shape. I've attached pics

Fluid after drain and about half a quart of new fluid to flush

Plug after cleaned

Metal shavings