AdderMk2

I found this on WebMD

Lead-footitis: Common side effect of a new aftermarket exhaust system in a mustang.




makes sense to me!

OnyxCobra

+1 When I first put my exhaust on i was careful b/c i wasnt used to it being so loud, but now i get on it a lot more often.

gbtrout

if its a used h pipe with cats make sure the cats aren't going bad.

ddeaton66

My money is on the O2's as well.

Twisted

Did you reset your computer? My car generally gets about 220 miles to a full tank in mixed driving, but after I reset my computer, it only gets 180 for that first tankfull. Then it goes back to normal. I'd run codes and then just drive it for a while and see if your mileage improves.

Swirl

I got about 150 - 180 on mine -

Swirl

AdderMk2

Its not uncommon for my car to get 250-270 to a tank

and thats usually re-fillin with about 12 gallons

P Zero

My gas milage varies depending on what gas I use. With premium I usually get around 250, mid grade about 210, with regular only get 180. +1, on resetting your ECU, itll force it to rescan itself and adjust as needed, usually.
-P.

Swirl

I am only getting 150-180 with premium - :\

Guess I really need to stop with the lead foot - :P

Swirl

ruger311

pull codes, get you some new O2s