Re: 92 stealth tt.. I think my ecu took a crap on me
if it's only running on 4 cylinders and a 53 code is in fact a bad PTU, troubleshoot the PTU. A bad PTU will do exactly that, shut down one or more coils. While your're at it, troubleshoot the coils. Sounds like you have a manual so troubleshooting these components is cake.
Lots of guys here immediately fault the ECU when the car starts acting up as sort of a catch-all. Yes, the caps go bad especially on 1st gens, but you said yours was a reman. Trust the code.
3si member #0440 (back when we got stickers and shit)