How can i do a vacume test to see if there is restiction in my exhaust ? also another quickie, about how much horespower am i looking at if i put on some aftermarket exhaust headers on a stock 91 tpi 5.7L ???

 

the metal air tube that runs to your catalytic converter..
unscrew the valve off the end and put a fitting or coupling on so you can run a hose inside the car to a sensitive liquid filled pressure gauge. Once you get your numbers take the gauge back off and hook the tube up as before.