Do a motor swap or put the money in the bank!!! It does not make sense to dump money into your D-series motor, it is a great motor, just not a great performance motor (without spending alot to build the bottomend). You could probably get a B16 swap and a few extra bolt-ons installed for $3K or maybe an LS B18 swap, some bolt-ons and a healthy shot of NAWWWZZZ (I love abusing that term) complete installed. The B18 would be alot fatser but not as reliable (especially if you are trying to race at every stoplight) but the B16 will have that fun, high strung top end. The GS-R and the H22 swaps are more than 3K (H22 swap is about 2700 but still needs the $500 mount kit and you have to deal with the extra weight), especialy if you need them installed.