Hey guys. So I picked up a 1990 5.0 Mustang the other day (sorry it's not an F150 question but I need help) and it had an off-road h-pipe on it. I got my shop to replace it with a catted pipe for state inspection. After I drove the car home and let it idle, smoke came out at a decent rate.

I saw that it looked like it was coming from under the car, but then I shut it off. This is freaking me out. The car ran good before the pipe got replaced. Could this just be an exhaust leak, soemthing burning off of the cats, or something else? Thanks for the help, this is really worrying me because I just got the car

 

if the pipe is brand new...hence the cats being new..it will burn off some smoke..when i installed my off road H on my 00GT i had some burning of oil due to the install and people putting their oily hands on the pipe..if the car is not lagging in power, or has any hesitation when driving you should be fine.

 

if you can do a cold start up on a cold morning, to see where it really is coming out of