In my experience the JP-2 was a great pipe on a .28. Nice wide tuning window, and big round gaping mid-range power. I have found the JP-4 good too. Easy to tune, and less of a fuel pig than the JP-2. There may well be some variables involved there, so perhaps the run-time thing is not %100..

I know a lot of people used to run JP-3's on .28's and liked them. I'm sure it would be good too. -2, -3, or-4... - all worth trying. I would expect the most power from the JP-2...