3.9 questions.
 

these 3.9 are strong buggers, but yet quirky too, lol. when you put your foot to the floor they do not go, but yet when you find that sweet spot they go like hell, lol. anyway I have a 2003 with 170k, runs good, no leaks, no smoke, I just want to step on the gas and go, not hot rod, all thou that could be nice, I just think these thing can be better. I am wondering about these throttle body spacers they say that help, also considering headers and cat back duel exhaust. what do you guy's think, worth wild or not? but I was thinking another way might be a turbo?

Throttle body spacers do not work on EFI. They do not make any (good) headers for the 3.9. As such, opening the exhaust doesn't do much.

The biggest improvement is to remove parasitic loss. As in, ditch the clutch fan in favor of electric fan, that is the biggest load. You can also get the Harland Sharp 1.7 roller rockers for the 3.9. The biggest change is to get it SCT or Syked tuned. Mine is with Ryan Hogan www.frptuning.com .

Don't you have to run 93 octane with those tunes?