weird problem with wheel size change

Not sure where to post this but my problem is that when I goto the track I put on my set of 15" rims with 225 bfg drag radials and roll 2 feet and bam my electronic boost gauge sits at -30inhg and doesnt move... the gauge doesnt start working again until I put my stock rims with stock tire size back on the car... how in the hell does this have anything to do with each other?

the electronic sender is hooked up to the stock boost gauge vacuum source on the brake booster. I also noticed on one run down the track, When i shifted into 3rd i had a really bad grinding type noise, possibly ABS brakes because nothing is grinding or acting up on the car otherwise... does the computer disable something with the ABS system when you put a different size wheel/ profile tire on? thats the only thing i can think of since the boost gauge sender is tied into the brake booster...