I am pretty new to jeepin and I heard that if you swap the intake manifold from a 95 or a few years newer into a earlier model (I have an 89) that due to the shape of the manifold it will give horsepower gain. The idea is that in 95 the emissions standards changed causing Chrysler to make engine modifications in order to pass the new standards. This however created a loss in horsepower, to compensate for this they improved the air flow in the intake manifold, gaining back the lost horsepower. This can be seen easily in the difference of the shapes of the manifolds (square to rounded). I was just wondering if there is any actual evidence behind this, and if so how complicated would the swap be? Would you have to modify the ecu system at all, due to manifold impacting air/fuel ratios? Thanks

 

first off you will need a 2000 year model manifold..amoung other things..do a search as i started a thread on this yesterday and it has just about all the info you need....

 

http://www.mallcrawlin.com/forum/showthread.php?t=6355

 

you can swap from a 1999 model.
i bought yesterday the november edition of the JP magazine there is an article of power true lies.
here a part of it.

´99-up horse power intake
MITH: according to that great wealth of information that is never wrong, the internet says you´ll get a 5to30HP gain thanks to the ´99 uo 4.0L´s swooped, equal lenght runners and larger plenum volume.
OUR THOUGHTS: while a free-flow intake manifold can deliver more horsepower, it is only going to allow as much airflow as the cilinder head and camshaft will call for.upping the intake runner volumetoo much will cause the intake charge to lose velocity, killing low-and mid-speed power and torque . on a ´98-earlier engine running a stock camshaft and unported cylinder head, it´s waste effort.
CLAIMED GAINS: 5-30HP
ACTUAL GAINS: 5HP loss on trasborg´s ´98 XJ (project milage master)