normally when i had the car it idled around 1300- 1400 rpms didnt know why, and the vac showed 15hg, so i turned the screw thats underneath the throttle body which was all the way open, dunno why either, and im reading around 11 hg, and car is running super rich and i have a crack in my downpipe, anything else can be the problem, i know it cant be bad compression cuz i car runs super hard and i did a 12.7 at the track. any ideas,

 

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My first drag race ever was a 13.3 @ 108 with two broken apex seals (broken before the drag run). These cars can run pretty well even with a cracked seal or two.

Do you have a ported engine? That might explain the low vacuum and rich mixture. Does it idle lumpy? Does the vacuum gauge needle jump around?

-Max

 

You only ran a 12.7 with a T-88 turbo? If thats the case I would be willing to say something could be internally wrong.