[Greg83]

Originally Posted by arpad_m

"Negative" pressure is (partial) vacuum, this is normal while the car is running with the supercharger bypassed (for fuel economy), the pistons create a vacuum that then helps suck in air via the intake, this is how all naturally aspirated engines work. Once the supercharger kicks in (when you give it some gas), it will immediately build boost, and on your LT4 you should see 9.7 to 10.2 psi.

Bleeding the intercooler circuit is a no brainer, make sure you get it done, as others already stated above. Unfortunately GM did not add a supercharger coolant tank from the factory, so you're at the mercy of whoever assembled the engine and filled the fluids to have done it properly, the only way you as an owner could check is opening up the S/C coolant loop.

I'd say let the dealer do it under warranty, and you make sure they know what they're doing, don't hesitate to go to a different service department if you see anything suspicious.

I’ll definitely try that after the fresh gas. Thank you!!!