The 4.0...are they all the same?

I have a 92 Sport 5 speed with 3.07's:firedevil and a 95 auto with 3.55's my father has a 99 with 3.55's now I know this could all be in my head but my older jeeps with the H.O. badge seem to have a bit more power. the 92 is a beast but thats the 5-speed and the 3.07's( I've raced a 5 speed with 3.55's and completely smoked it like 4 car lenghts) I've beat several V8's and countless rice burners. Are the newer ones MPI or are all of them? or did they do something to change emissions? I also saw the newer ones reccommend 5w30 instead of 10w30.

http://jeephorizons.com/tech/xjstockspecs.html

something of notice - engine specs and weights. if you look at the body style changes, anything 94+ is probably heavier b/c of the safety and strengthening features added.

Extra emissions were added in 2000 and I believe in 1996 they changed slightly too. 1999 or 2000 is when they added the "precats" which might have something to do with it.

could be lots of things though. are they all stock? the 5 speed is nice b/c you can control when you shift, so you can probably get better torque. driver has something to do with it too...some people just dont know how to drive!!! or they might need a tune up, oil change and new cat/muffler/exhaust manifold/air filter....

Not just that, but i believe the heads (casting number 7120) that came in the 91-96's were better flowing. Then of course in 97 they added even more emissions stuff so that didnt help. A well taken care of RENIX (87-90) does pretty well also. Although the heads on those suck.