Quote
the throttle may be partially closed, so the engine is pulling against less that 14.7psi in the manifold.


Note you should test the Compression with the Throttle all the way down.


89 Monturbo (RIP now but the heart is in the 90!)
90 Montero with 2.6 turbo swap! (close to finished)
88 Starion MPI T3/T4 Magna M8 head.....
96 Volvo 850