I drive a 2000 Jeep Cherokee 4.0. The engine was rebuilt, every electronic sensor replaced, engine harness rebuilt, new fuel pump etc.., basically everything has been restored on my XJ and I still suffered from the same rough idle and loss of power for over 2 years and could never figure it out! This smoke machine resolved this! The first leak I found was in the trunk, the vacuum line to the rear wiper motor was leaking. I deleted this wiper motor a while ago. I used the air pump for this leak and heard noise from out of the line that was dis-connected, I never knew that the wiper line was a vacuum line that went directly to the engine whoops! So, this was resolved quickly. BUT I still had an issue, I ran smoke through all the lines and tested the vacuum valves etc.. come to find out the vacuum valve on the passenger side was leaking, I replaced, re-tested, and no smoke was coming out, just drove 500 miles and now my idle is much better and I have full power re-stored! This smoke machine did a fantastic job!!! The only thing I slightly disliked is when filling it up with mineral oil I overfilled it, it was hard to see how much was inside through that little glass window, so be careful how much you put in. But overall, I highly recommend this smoke machine, it freakin works and saved me a ton of money from almost paying a shop to diag it for me!