The car feels weak above 5k and backfires when I abruptly let off the accelerator. Below 5k, it's perfect. It's throwing P0302 though. I've already replaced the coils, plugs, wires, cleaned ESS, MAF, and IAT. I also have a rattling CAT that I will be replacing (it's not blocked yet, I removed it to check), but I want to fix this misfire first. I had a stuck intake runner valve that was recently fixed, and that code is gone now (thank god). This leaves me with P0302 and P0420 (the cat). What else could cause P0302 besiides the fuel pump?

Thanks y'all

 

Fuel injector, blown engine

 

I don't think it's the engine, because it runs great below 5k and doesn't have starting issues

 

Seems like you've knocked off the usual suspects.
Not sure if it will help, but check this thread https://www.rx8club.com/tech-garage-...t-here-222280/

Have you actually verified that your engine is healthy? Compression test could help, if all else fails

 

No I haven't. Dealer wants $120 to do it and from what I understand, compression issues begin in lower RPMs first and my lower RPMs are flawless. I will have the fuel pressure tested soon though. And yeah, I know that thread practically by heart :/