Combines booster preasure

first i would check that all plugs are tightly screwed into the intake manifold, i had come one out years ago and it did the same thing. use some pipe dope or loctite and get it tight. second, check all fittings on the boost guage, both ends, the gauge and on the manifold, and then start checking your turbo and gaskets. I used an m2 for twenty years, had approx 4200-4300 hrs on the motor and never had a problem with the turbo. pulled as much as 22-23 lbs shelling corn in the mud with big tires, rwa and high yielding corn. wanted more power but the dealer said he couldn't advise turning up the fuel anymore than it already was. my two cents worth James

I took the line off at the manifold and threaded some fittings together so the guage line went through a spray gun regulator then to the air hose. Turned the air on to about 20 psi and listened for a leak in the line running to the guage. After fixing the hole in the line the guage responded to the regulator changes in pressure

Same comment here. Had an l2 where a plug (1") came off on the back side. Had to go in thru the grain bin access to see it though.