i did it and i was having issues with the coupler not staying put, so i bought a new header and left the cone on it. . .and i personally suggest you do the same thing, and it really doesn't do that much if anything to the performance
If I had to guess I would say the racing pipe. I put a resonator on mine, and they have different tuned pipes for what you're looking for.. if its bottom end, mid, and i think top end power. It doesent hurt to look. My resonator made a significant difference in performance
I'd agree with steel city nitro on this one buddy, really the only thing you can do is do some research on what pipe combo works best for what you want it to do and make you purchase decision from there.
The THS pipe is the best race legal pipe I found. Very broad powerband on 3.3's and OS 21 TM's. Def. made the engine tune easier, but it did require a bit richer needle settings on the 3.3 vs. the stock pipe.