I think there are a couple threads like this already. Try searching for the topic and you will probably find tons of info.
But in the mean time, I would say rear head cooling mod, 'j' mod which is the tailshaft lube mod mentioned above, Drive shaft if you havent already done one.
2003 MARAUDER ---SOLD---
-MOD LIST-
Ø MMR Race 1100 shortblock, Polydyn coated pistons
Ø Pro Turbo Systems turbo kit with Precision 76GTS turbo with polished H compressor housing
Ø Ford GT Complete Cylinder Heads (Cams, Springs, Retainers, etc)
Ø Twin Ford GT fuel pumps, -8 braided stainless lines and billet rails
Ø Custom All Metal Cowl Induction Hood