Flowmasters actually completley kill hp on high powert cars, I was reading a test where they bolted some onto a 1000hp supercharged corvette and they choked it down over 200hp over just 3 inch glasspacks. But on a supra, Youd still gian quite a bit of flow over the stocker, But yes a straight through glass core or other type of muffler will flow best, and also be loud. Heres a video for your listening... 2.5 inch meinike exhaust pipe, magnaflow 2.5" fiberglass core muffler (very stright through, you can see out the other side) and a stock 7mge...
http://videos.streetfire.net/video/4...3600db0c59.htm