So I got my wsp Y installed about a month ago, and now my mileage just plain sucks. I went from about 20 mpg before to less than 16 after. Is this common? I don't THINK i'm driving it much harder than before. What could be causing this? I might call WSP.

 

it shouldn't hurt your gas mileage at all, it may even increase it a little

maybe your O2 sensor got damaged (or not reinstalled) when they put in the Y pipe

that's the only reason I can think it would go down that much

 

gotta be the O2...did they put antiseize on it before reinstalling it?

 

Well I watched them reinstall the o2 sensor, and i don't think they put any seize lubricant on it. Why would it matter though?

I'm going to feather throttle this tank and see what happens, then let you guys know. It does seem like there should be more power, too. Would the o2 sensor cause any power loss for any reason?

 

If the O2 is bad, can run on the rich side, yielding poor fuel economy AND lack of power.