The 98 ZJ's are none EGR. I owned a 98 ZJ 5.2L Limited for 9yrs & loved it. Sold it for my JK & still miss it. Always wanted to put a different intake on it because the Big Bulky Magnum intakes were good for low end tork but suck at anything over 4500rpm's. The improvements that I made to it were Borla cat back exhaust(not much noticed), AEM Cold air intake(huge Improvement),Flex-A Light 180 electric fan(huge improvement)Reved much faster & A/C worked much better at idle,Jet performance stage 2 chip(got for free & noticed nothing till installed 180 T Stat that is suposed to be installed w/Chip & that is when I noticed a small improvement), MSD ign wires & coil,Acell cap,rotor & iridium plugs(noticed huge improvement due to stock mopar ignition parts just plain suck), Deep sump trans pan w/drain plug(8Qt) ,large trans cooler & in line filter before cooler to stop any debris from cloging cooler in radiator(they clog very easy) Your trans will love you for it. The trans is the weak link in the ZJ but if you keep the fluid clean & cool it will last a long time if it is in good shape before you do this to it. If it is the 5.9 Limited(only offered in 98) then it has the Full size truck trans(46RE) but the 5.2L had the 44RE witch is the same as the 42RE behind the 4.0L but w/extra clutch disks & stiffer springs in the clutch packs. Sorry for the overload in info. I loved my ZJ. So yes I think the intake should make a sizeable improvement but remember this that the largest restriction in the 5.2 & 5.9 is the heads. Headers make a nice improvement because I have driven a 5.9 Limited with them & it was noticeable but the heads are holding this motor back in a MAJOR way.