I've tried a number of different pipes and the JP-1 is one of my favorites so far until I can get my hands on the Odonnell pipe ... But until then the JP-1 and the Associated 2035 are both good.

I've also put an aftermarket OD head on my SS 21.. I did lower the temps, probably because your getting a reading further away from the plug, but you have to open up all 5 holes on the aftermarket head a little. The 4 mounting holes are wider on the engine, and the center of the button where the plug goes in is also wider, but it works fine...