Any upper or lower block learn limits?

[we4Mateo]

So if there is a vacuum leak and things are not working right would gas mileage suffer?

It would have to be one hell of a leak.

 

[Gary Wells]

My 34K mile '87 turbo Buick is down to 14.06 MPG, with some of that being freeway & some city driving. I did find a very small vacuum leak in the switch that sits on the charcoal canister where a outlet goes down into a small hole in the top of the canister. It uses a "O" ring to seal it, and when it was installed the "O" ring was not lubed, thereby not allowing the outlet to seat full depth.
After removing the switch, lubing the "O" ring & installing it up where it should go, the motor smoothed out a tad & appears to have picked up about 1 or 1.5 " of vacuum. Right now I getting about 18.0-18.5 " of vacuum. My BL runs about 134 at idle starting up, and then drops down to about 128-131 or so.