Haha ok so I have been trying to fix this rough idle since I bought it. It seems as if my mpgs have taken a hit also.
99 XJ 4.0 aw4

heres a list of what I've done

Fuel injector cleaner in tank
Cleaned IAC/TB
Fixed header/exhaust manifold leak
New plugs cap rotor wires
Champion coppers.. gapped .35
New upstream o2 NTK
Checked all vaccum hoses brake booster stupid ball under fender (moved from bumper) all look good
sprayed carb cleaner

I am going to oreillys to rent a fuel pressure guage and check it

Heres a video dont know if it'll help any but hoping so you can hear it knock a little at the beginning

 

Sounds just like my 99'. My idle is rough too though. Sub'd.

I know I have a exhaust manifold crack though. I'm not sure how much that after the idle. Did pretty much the same maintenance as you less the (fixed exhaust leak)

Running refurbished fuel injectors too. Didn't help rough idle but did give it a much faster start and seemingly better MPG

 

Whats the ideal fuel pressure I am looking for?
I need to get a multimeter too so what sort of readings am I suppose to get on my TPS and what else should I test?