1984 Nissan Maxima, 2.4 inline six cylinder, Very low vacuum, no power, Help!

[jlgood50]

Hey Guys,I have a 84 Maxima wagon that is only pulling about 10" of vacuum. I replaced 90% of the vacuum lines, replaced the intake/exhaust manifold gasket. Another problem associated with this is, when you remove the oil filler cap the engine stalls out. You can feel the suction while lifting off the cap. I replaced the EGR valve and checked the PCV valve. It seems like the engine is not ventilating properly. It idlles rough and has extremely low power taking off. Once you get it up to 55-65 MPH it does run better, but still not as it should.The car has 185K on it. Did a compression test and 4 cylinders were 100 psi and the other two were at 90 psi.It uses about a quart of oil every 2500-3000 miles.I really like the car and hope that I can figure out what the problem is. The mechanic that helped me said he is totally baffled as what to look for next, as he has never seen an engine stall by removing the cap. I appreciate any help you that you might render.Thanks,Jim