98 Intrigue - engine won't rev above 4000 RPM in drive

Hey all, so I bought this car as a mechanics special a couple months ago. Engine needed a new intake manifold and the timing cover was off for some reason, so I threw a new chain and tensioner on while it was open.

Finally got everything put back together and it runs really good, but it seems to lack power. If I floor it, it takes a good 8 seconds to get to 45 MPH and that's about as fast as it'll go. The engine will get to 4000 RPM and begin to stumble as if it's hitting the park/neutral rev limiter.

Whats going on here? Does the ECM think I'm in park? Did I get the timing wrong? Fuel supply problem?

Could be a bad cat......

Thought about that as well. I noticed the exhaust manifold gets awfully hot awfully fast. I think I'll investigate the cat further...

Could be a bad cat......

Ditto. Some have a removal bung(test port) in front of the cat. It may have 1 tack weld to keep it from unscrewing. If so, remove and see what happens.

BTW, drove it again today and when I floored it, CEL started flashing and it dinged at me. I've got code P0300 now, random multiple misfire.

I changed the crankshaft position sensor since the harmonic balancer was off which I realize now may have been a mistake. I didn't know you had to do a relearn after that. Would not doing a relearn cause such a lack of power?

Check the cat first.

Thanks everybody! It was the cat. Loosened the bolts holding it to the exhaust manifold and it ran much better. Finally got time to put a new cat on today and it runs like a totally different car, easily goes over 4000RPM and shifts better too.

Still getting P0300 when I floor it though. Gonna change the plugs and see what happens. Not sure it'll fix anything, I have a feeling it's fuel system related. Already swapped coils out with no luck.

EDIT:

Fixed it! It was a faulty ignition wire. Started pulling plug wires and one left its guts behind. I just bought those things too... I put the old wires back on and this thing will burn rubber now.