[Kevin McClelland]

Floyd, with the Flowmaster mufflers it has nothing to do with back pressure and everything to do with placing the vacu-pan nipple in the muffler. Through many hours of testing on a flow bench and on the engine dyno with a 540 big block the most vacuum we were able to create was 1 inch of mercury! This was a day of testing of different angles cut on the end of tube, location of tube, angle of tube, and all the testing was done in a straight pipe (i.e. collector) not in a muffler.

Sorry guys, didn't mean to take up a Pontiac thread.

Kevin

P.S. Bruce, did you ever get the turn downs you were looking for? One of my tech guys said that he had spoke with you about them. Take care.