Ditto on the dubs, the handling will go to crap. Get lighter wheels and (better)tires(turn the Stones into tire swings)stick to no more than the 18's you got...wider though...265 or275 won't cause much trouble . Get a set of nice,steel,brakelines and you're on your way to making a great car better. Pull the back seat (unless you REALLY need it)bloody useless anyway.Get runflats...ditch the heavy,inconvient spare. You might look into a CF hood insert, and lose the weighty OE one. Last, dump the 55gal. drum of a muffler Isuzu gave you...something throaty but not obnoxoious. KEEP THE STUFF YOU TAKE OFF/OUT. none of these changes void or harm anything and can be easily undone. did I say get a K&N airfilter? Get a K&N air filter. These are the few things I've done (plus change all lubricants,grease and all, to Mobil One. My times improved,no problems at all,and now with 21000 miles,it is getting 21 and 22 mpg routinely! This is flat Florida. Think light. MY $.02.......Wayne