Vac leak and plug issue!

[Rieger_RS4]

I have a set of NGK pregapped ecs plugs (not the colder plugs for chipped cars) and also i set of Iridiums. What should I gap them to if i have an APR chip? Also, i think i have a vac issue. when in park or neutral it reads a perfect 20 but when i shift into any drive gear it drops to 16 and if the ac is on it drops all the way to 12-10, and the car begins to vibrate a little with or without the ac on, but more witht he ac on. Whats wrong? i replaced the BPV to mani and FRR to many vac hoses. Are there any other ones?...and why does the vac change when I shift into drive gear? Also, with my 1bar apr chip, I have a very hard time reaching 1 bar(only on wop) and most of the time I get 5-8 douring normal driving. WTF?

[Zodiak]

vac changes when you shift into drive because you're basically in1st gear, if it was a manual tranny and the clutch was fully engaged in first gear and you didn't give it any gas, the car would stall. Being an automatic, the car gives it more gas to keep it always engaged (notice that if you take your foot off the brake while the car is in drive, the car starts moving?). That's one of the reasons cars with manual trannys boast better fuel economy, in traffic at a stop we're in neutral, vs. always lightly engaged in first. Granted the automatic transmission is much more complex than this, that is the easiest way for me to explain it (it's also 4am over here).

[Rieger_RS4]

I see,

but why does it start to vibrate very slightly when in gear? and even more when ac is on.........and with ac on the vac is at 12-10.

[Daft]

all cars will "idle-up" when you activate the A/C compressor. The car knows to do this so that it won't idle too low from the extra drag on the belts and stall if you come to a stop. Having your vacuum read in the 10-12 In Hg zone while the A/C is on, is very normal.

[Rieger_RS4]

k, sound good.

what about the minor vibration with ac on?

Is that also normal?

[4ingDrive]

Totally normal. Mine went away when I added the SPP efk.