I just bought my 5th F body, a 1990 F150 4X4 5.0FI to go with my 87 F250 and my 90, 91, 93 Bronco's. I took it thru our state inspection today and they told me there was not enough exhaust at the tailpipe to test the emissions. I thought they only complained when there was too much or too loud at the tailpipe. It runs OK and I had it to 75mph on the way out there. It has the factory twin converters on it. If one or both converters were so clogged that there wasn't any exhaust at the tailpipe then I would think it should not even get up to highway speed, would it? I felt it at an idle and there is exhaust coming out, not a tremendous amount but still you can feel it. There aren't any holes in the tailpipe after the muffler either. Any suggestions? Has anyone had any luck with any of the converter cleaners? I'm willing to try anything short of replacing another $300 "Y" pipe with converters like I had to do on my 90 Bronco.

 

use a vacuum gauge to check backpressure. gauge will have instructions or look in a haynes or factory manual on how to read gauge.

 

LOL - Just tell them you're running hydrogen and oxygen and the only exhaust is air and water

 

I'd like to try it. Here the motor V guys are on a real power trip. You can't give them any crap or smart mouth or they will pick your car apart. It had one of those long round mufflers so I replaced it with a new short one. Now they are happy with the exhaust but it failed the emission test miserably. The HC was so high I suspect a bad intake manifold gasket.