Rough running

I think I would pull out the multi-meter and start testing electrical, camshaft position, crankshaft position, MAP, IAC, Air Intake / Charge Temperature, Knock / Detonation, oxygen & speed sensors and timing belt old or worn, Throttle body and IAC dirty may need removed and cleaned and new gaskets, low Vacuum, Low fuel pressure or dirty fuel filter, Computer may be in limp mode for reasons that a part is not sending signals or bad computer, have it scanned for codes too.

May also check intake gasket. Also head gasket.

BTY these are known clunkers and are bad cars.

PT cruisers are wonderful cars they have gotten a bad name because they are hard to work on because of the lack of space in the engine compartment. I have a PT CRUISER GT TURBO and love it just like any car they require maintenance. They have quirks but can be figured out. There are many videos on You Tube to help you. It prob is the mass air flow censor or as the first person stated MAP they tend to go bad. Good luck don't give up. They are worth the extra work!! (This is an easy fix you can fix yourself watch the videos.)