It works more like an open header on a 4t. The exh. valve will prevent complete scavenging, but it does empty better than a baffle set up. I don't care for the tone on a 4t tho! it sounds like one of those jap cars w/ the trumpet exhaust. To each their own... Quite awhile ago I was looking for open header lengths/tubbing diameter ratios for slinger, and never did find a formula. If anyone has a clue on this it may help for the weekend drag strippers. Muffler off/pipe on, win a drag, pipe off/muffler on...