We are still using the same K&N filter element, but have had to replace the air tube twice now.
The Borla stainless steel headers have loosened their bolts numerous times, resulting in two blown gaskets. They're not fun to replace, so we're more conscious of putting a wrench on the bolts at each oil change. As to oil changes, it's a major chore to sneak the oil filter in, out, and around the headers, even with a shorter-than-OEM type filter. This is such a problem, we're not sure if we would put them on a V-8 Grand again, but the performance gain from the headers is really remarkable.
The only other engine modification we've made was a K&N air filter. Performance was enhanced by this addition that equaled the Borla exhaust. The plastic air tube, where it attaches to the throttle body, had warped and thus didn't seal properly. K&N has subsequently solved it with an embedded steel ring which we have changed to. Between the exhaust and filter change, we dropped over a full second on our 0-to-60 time.
The IPF rectangular lights still reach out for distant viewing on those long winter nights, and we're surprised their lenses have held up to flying rocks. They are definitely tougher than the windshield, which we have replaced several times. (It's well known that you can count the winters you've lived in Montana by the number of windshields you've replaced.)
The Wet Okole Hawaii seat covers have surprised us in how well they have held up. In fact, they still look like new, and so do the factory seats under them. The Nifty Products' Catch-All floor mats also have done their job well. They're at the point of replacement now, but we hate to think what the factory carpet would have looked like had they not been there.
Without the nerf bars from Off Road General Store we would've spent a lot of time repairing rocker panels. | 
Other than a bit of rust on the shock bodies, the Rancho RS 9000s still maintain ride control after 75,000 miles. The Air Lift airbags failed after just more than 30,000 miles, most likely due to our excessive hard use. | 
The Borla stainless steel headers and exhaust system was a positive benefit in power increase, but they sure made it difficult to change the oil filter. |
Exteriorwise, we had added EGR fender trim; we hesitate to call them fender extensions as they stick out less than an inch. They have sacrificed themselves to several rocks and trees, protecting the body while absorbing the impact and still holding up. However, the rear air deflector doesn't do squat for keeping the liftgate's glass clean. The front deflector at least keeps the rock chips off the leading edge of the hood. The side window pieces are nice, in that a window can be lowered an inch or so for parked ventilation without the worry of rain getting in.
For rocker guards, we finally settled on pieces from Off Road General Store, which is now part of JKS. Without them, we would have spent several times their initial cost in bodywork to fix the damage we would have imposed. They're a real necessity.
What We're Going To Do Next
Yep, we're going to make our Grand Cherokee even grander-in a big way. These changes are going to allow us to go places that we've always wanted to but didn't feel that the vehicle was up to. Besides that, now that it is done, it looks really cool.
First, there is the all-new unique prototype long-arm suspension and 5 to 6 inches worth of lift that we've been working on with the folks at T&T customs in Cheyenne, Wyoming. It's not been easy working out all the bugs on this, especially since it also includes a front and rear axle swap, ARB Air Locker up front, and an Eaton electric locker in the rear. The suspension lift allowed us to upgrade to some 33x12.50s on aluminum rims, with the potential of 35s perhaps in the future. These changes, as you can imagine, greatly enhanced the off-highway travel ability of the Grand and improved ride quality. Because of the subframe modifications, we also had to have TNT Customs build us some new rocker guards/nerf bars for the sides. These are future production models with a modification just for us. Tomken even updated the spare-tire holder so that it no longer rattles.
These aren't the end of the modifications that will happen as we progress on this project. Next month, we'll commence with the buildup.