96 running poorly

I was hoping for some insight.
I have a 96 with the 4.0

I replaced (after a few headaches) the motor mounts with brown dog mounts and the transmission mount with an oem.

Also replaced the exhaust manifold with am atp header. Once it was all done last night, I took it out for a test drive and it sputtered a little but then seemed to drive fine, maybe a little sluggish.

When I went to drive it to work this morning, it started up a little more rough than normal and it definitely had a loss of power.
It also wouldn't go over about 3200 rpms (got there very slowly too). When it up up to 3k-3200, it would act like it was hitting the Rev limiter and wouldn't get up to highway speeds.

Then, when I'd let off the gas, the motor would stall. All the electrical was fine and my gauges read like normal. It would start right back up, with a rough, low idle. But I was able to limp with home. It died from letting off the gas probably 4 times in the mile or two getting home.

It's still acting like that tonight, so I came here looking for some possibilities. Everything that that can find as far as connectors are plugged in.

The only code I'm getting is for the map sensor. But that code has shown up intermittently for he last couple months with no ill affect on performance.

He only other thing I did was take out the transfer case drop off the crossmember. I already have a sye and am planning to measure for shims. I'm getting no obvious vibration from the drive shaft as of now.

Any ideas?

What you described is a bad MAP.

Is oem the only good one? Or would other brands (spectra specifically) be worth the money?

Ok. I thought I'd, make an update.

I replaced the map sensor, now it idles better. I still can't get it over about 3200 rpms, but now it doesn't die when I let off the throttle.

It's still pretty lethargic when I try to accelerate, and it doesn't really want to downshift.
Also, I noticed a thinking sound when it wanted to downshift that waset there before.

It's also now throwing codes for 02 and toss.

It is possible the cracked header was hiding those? Itsort also cranking and starting better than it was.

Any ideas?

The only thing I didn't put in my original post is I DID remove a one inch transfer case drop.

I'd check the O2 wires and connector. I'd also make sure the O2 harness hwere it runs up the from of the motor isn't touching the exhaust manifold.

Replaced the 02 sensor, which cleared all the codes. Then...the xj started blowing it's and relay fuse, so it's either the relay or probably wire touching the block from the o2 sensor connector. Just haven't had time to look