93 Emissions issue

Hi folks. Did quite a bit of seaching, but have come up a bit short. Short version: failed emissions (sniffer) on all measures. New to me 93 Cherokee, 4.0, 198000 miles, header, looks like a 99+ intake, 5.5" lift, D30 front/8.8 rear, 4.56 gears. Here's what I have done so far: new plugs, wires, coil, dizzy cap and rotor (good spark), fuel filter, ran some seafoam through the intake, oil change (5w 30). I thought the cat might be bad, or hollow. I can't get any measurable backpressure on the engine side of the cat. Might be the way I am measuring or the gauge is crappy. Measures vaccum just fine... But, the temp difference between the front and rear of the cat is almost 200 degrees, maybe more which points to something else. Need an opinion, replace the cat or ? The 99+ intake has me wondering about the MAP. Maybe put in an adjusable MAP? Any help or input is appreciated

What were the numbers on the test?

If MAP was bad the engine would run like crap. 99+ intake with header usually has clearance issues and vacuum leak so maybe check that.

But without seeing the actual test numbers it is hard for us to give you a starting point.

Dang it, I knew I forgot something: HC gpm:2.82 (limit 2.5), CO gpm:30.45 (limit 25.0), NOx gpm:5.91 (limit 4.5). Also, this test was after I did the mild tuneup. I did replace the 02 sensor as well. I am fairly certain that MAP is not bad. I was thinking more along the lines of trying to dial in the air/fuel. Although, I would rather not. The Jeep runs just fine.

Thanks

bump..

High NOx is the result of combustion chamber temps too high.

High HC is running rich/unburned fuel.

High CO also points to running rich/unburned fuel.

Don't see anything about the o2 sensor being replaced. If there is an intake leak or an exhaust leak upstream of the o2 sensor the PCM will read the o2 output as "lean" and enrich the mixture. An intake leak would lean the mixture and raise NOx.

May have a few issues going on.

o2 sensor has been replaced. Done at the same time as the plugs, wires, etc. No noted intake leak, or exhaust leak. I will recheck both this week and hook up the vacuum gauge to be sure I am not missing something.

Thanks