I just installed a vacuum gauge on a 91 350 tbi and im getting a reading at 10hg at idle and 0 at wot.

I know that ive got oil leak at the rear of the intake but i didnt think that that would mean anything in vaccum wise.

Also i didnt really know where to tap into to get a vaccum so i put the tee in the line between the tb and pcv valve. I dont know where else i could hook into other than the brake booster but i didnt want to do that kind of a reduction.

Its a truck motor if theres a difference

10in-Hg at idle is way low for a stock engine. Should be closer to 18-22in-Hg.

0in-Hg at WOT is normal. Remember, the more load on the engine, the lower the vacuum.