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If you want to find that ellusive intake leak then follow this procedure. You will need a leakdown tester and PVC cap (2 1/2 I think). Drill hole in PVC cap for the leakdown tester. Remove up pipe, leaving the rubber hose on the TB, and tighten PVC cap on TB. Remove valve covers and rocker arms. Nice time to inspect for broken valve springs, hammered rocker arms or busted plastic stops in the shaft. Connect the leakdown tester. Adjust for about 20 PSI if you can. The test on my GN showed I was putting in 20 PSI but holding 3 PSI. Get some soapy water and hit the intake gasket and watch for bubbles. The worst place is the TB seals and the metal vacuum block. I put my plastic block back on. I have checked 3 so far and each was a bubble machine when I sloshed the soapy water on the TB. Also a great way to check the one way valves in the vacuum lines.
You can find an exhaust leak the same way. I bought a rubber coupling and PVC cap to put on the downpipe where the cat was connected. About 20 PSI in the downpipe and hit the headers with the soapy water. My headers are leaking between the header tube and the flange. My flanges are leaking so bad that I put in 40 PSI and held 2 PSI.
 
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