the only place smoke came out was the air cleaner box.


Then it is not testing for much, other than for holes that are bigger than your throttle body. There is no way that thing pressurized the intake enough to check for vaccuum leaks. I guess it could check for passive leaks and really badly cracked hoses or unhooked hoses, but definately not going to tell you if the IMG is cracked.

OK, I searched a bit on these machines. a) You should have blocked off the throttle body or air filter. b) It may not be a very high pressure. 1-2psi max. Again, I am not sure that is enough. 3) These things seem like your average shop scam. One article talked about using the smoke machine on every vehicle and then trying to upsell the customer on what they find. Is it mechanically correct? Yes. Is it diagnostically correct? Debatable. Is it fishing for business? Yes? Ok, I'm off my soap box on that one.

I would get out the carb cleaner or propane on this one. I think Rubo's suggestions are good, but remember, we got a lot of history with bad IMGs on Isuzus. There are better ways to diagnose the problem than that smoke machine.

Good Luck,
Michael