You are getting a misfire because of the vac leak. We have boost gauges for a reason. You are way over thinking this at idle you should be a 20in/hg. That proves you have a leak. Pressure test the system, find the leak and bam problem solved. Under negative vac you are pushing metered air out under positive vacuum you are sucking in unmetered air. What you are doing now is wasting your time and money.