Cressida 1uz swap running terribly

[BoxyShazam]

I've got an 88 cressida with a 90 ls400 1uz in it. It was running great for 4-5 months. One day on the way home from work I noticed it was a good bit slower than before. Over the next week it got worse and worse. Now I can't even drive it anywhere because its so slow.

It's throwing codes 21 28 and 55. Thrown these codes as long as I've had the swap. Intermittently gives codes 14 and 15. This may be caused by me unplugging the coils and igniters to test them. Maf checks out. New high flow fuel pump. Getting 12.5 volts at the fuel pump. Coil and igniters seem ok but haven't done a definitive test on them. Unplugging either causes more issues. It's not in limp mode as far as I can tell because the timing is where it should be.

Any help is much appreciated!

Edit: forgot to mention I did a compression test and it came back very strong at 175-195 between all cylinders

 

[Bushwhacker]

You need new O2 sensors.(codes 21,28)
55 is a knock sensor code. This could be the reason for poor performance, severed wire?

 

[BoxyShazam]

I am aware of the codes and their meanings but like I said they've been there since the beginning. Could itreally take 5 months for the code to cause any problems?

 

[BlackUZZ31]

It wont throw codes for no reason! have you checked the plugs, leads, fuel pressure, injectors cleaned?

has it had a cam belt change, is the cam timing out?

 

[BoxyShazam]

Yes I checked all those things except getting the injectors cleaned. Sorry I didn't post more info, I didn't want to clog up the post too much.

Found the issue. It was a very clogged cat

 

[litldv8]

why was the cat clogged up?

 

[Bushwhacker]

why was the cat clogged up?

Furball?

 

[BoxyShazam]

Yes it was a giant furball lol. No the catalyst had busted and become an obstruction. I got the cat at a little Mexican exhaust shop super cheap. There was only about 3/4 of an inch cat material on each end and the rest was hollow. Very poor quality. Not sure If it melted and busted up or if I scraped too hard and broke it. Either way its test pipe time for me. Thanks for all your help everybody