[PJ]

You can start with the downpipe and exhaust. I believe the stock DP is cast iron from the factory and a light-weight aftermarket exhaust saves about 40lbs I think. Some nice ones...

http://www.greddy.com/prod_racingtt.htm

http://www.hksusa.com/products/?id=1155

http://www.apexi-usa.com/product_exhaust.asp

http://www.blitz-performance.com/Blitz_Ex_Spec_R.htm

http://www.rs-r.com/products/exhaust/gt2.php