Help needed - vacuum leak, need retorquing intake manifold on M117

[Bondavi]

I have reason to believe my new intake manifold gaskets are leaking vacuum. I torqued them to 20 ft/lbs, and am seeing seepage around #3 cylinder. Vacuum gauge reads 1/6 off fully pegged position at idle (700 rpm), timing is set right but as ROM's climb, the vacuum advance goes out of whack (35+ degrees BTDC around 2000-2500 rpm, rather than the specified 25 degrees). I thought it was maybe a faulty fuel injector seal, but don't think that one injector seal could cause that big a drop, could it? All injectors/seals/insulators are new, BTW.

What is the correct torque spec and sequence for manifold gaskets, I read it is 18-22 ft/lbs. Should I set to 22 or slightly higher like 24-25 to "re-seal" the gaskets?

When I did the job, I started with the center bolts and did it outward alternating between sides. I suspect when I removed 1 or 2 of the bolts in that area of the leakage to change bolts to a new one AFTER torquing it in that it did not "reseal" after the initial 20 ft/lbs then back at 20 ft/lbs. Can I do one side starting from the center then outward, alternating, and then do the other side when done? I did alternating outward between both sides when I first put them on.

Any suggestions? Thanks!