This truck — is it a "truck"? — has the 4.7L MPI V-8, is a 4×4, and is the "Limited" trim package with nearly every whiz-bang option available. I bought it because I needed a 4×4, and this turned out to be a pretty good deal even all those options not withstanding.
So far the only thing I've found is an exhaust system by Corsa (who I know nothing about) and a lift kit by a company I've never heard of. It appears that the performance market only cares about the 5.7L Hemi that was available for models years 2005-2010 (Jeep code is WK for these models).
The engine that the truck shipped with (according to Jeep) 230 horsepower and 290 lb. ft. of torque. I am replacing a Ford F150 that had over 300 of both, and am interested in any options I have. I also had the F150 lowered, so I know nearly nothing about good companies for lift kits. Pro Comp and FABTECH (the only off-road suspension companies who's names I know) both have no suspension upgrades available for the '07 Grand Cherokee (or any Grand Cherokee).
- 2" – 4" lift
- 50 – 100 additional HP/torque through "bolt-ons" (headers, exhaust/high-flow cats, chips, throttle bodies [although it's multiport fuel injected so I don't think I have one of those], air intakes, etc.; no superchargers, cams, or heads — at least not yet)
The Jeep forums I have found are amazingly short on content when it comes to the WK models. It appears people only care about modifying Hemi engines and Wranglers. When I buy components I generally ignore price and look for comprehensiveness and quality. If a lift kit from A just includes rear leaf spring blocks and longer U-bolts for a 2" lift, but a lift kit from B includes physically upgraded replacement leaf springs, urethane bushing replacements, new bolts for all the hardware, etc. and gives me the same 2" lift I'll go with B (assuming B is quality parts).
I am generally handy with a wrench but I am not a mechanic. I installed my own replacement front/rear springs/hangers and shocks on my F150 (a kit from Eibach) and have done short-throw shifter, headers and exhaust on a Ford Ranger I previously owned, but when I had to replace a transmission in that same Ford Ranger I leaned heavily on the expertise (and much larger tool box) of my father.
I am not a crazy off-roader, but I camp often and drive through the deserts of Nevada and California frequently so I'd probably be served fine by a kit that was just leaf-spring blocks. However I also have the personal motto of "go big or go home" so I'd take a much higher quality and more comprehensive kit that I'm unlikely to fully use over the cheaper alternatives.