I have magnaflows on my GP STE. I just put them on a few days ago, and they made a huge difference. (but my stock mufflers had big holes in them, so it sounded crappy anyways) They are straight through mufflers, so they flow REALLY REALLY well, almost as if they were straight pipe, but they aren't very loud at all, much quieter than you would expect for being straight through. The car sounds very deep at idle, but its still quiet, not that wake up the neighbors noise. Then when you rev it up, it doesn't get any louder, the tone just changes, and it still says fairly deep and makes it sound a little like V8, which is quite an accomplishment for my little minature 3.1L V6. Its not like most mufflers that sound deep at idle with a V6, where when you rev the engine up past 2000rpms it sounds like a 4 cylinder. They sound very nice, and I am very impressed with mine, and I am more and more impressed with them everyday. You can't beat the lifetime warranty either. Mine were $45 each, which I think they were WELL WORTH for what they are. If thats what you think you want to get, GET THEM, don't change your mine. You won't regret it.
1990 Maroon Grand Prix STE McLaren 3.1 Intercooled Turbo, 14.695 @ 94.49 on 12psi before cam/heads/etc.
1990 Bright Red Grand Prix McLaren 3.1 Intercooled Turbo, 14.819 @ 92.72, 189whp
1999 Grand Prix GT 9.75:1|K&N|160 tstat|No Ubend/Cat/Res|UD Pulleys|Ported M90/TB/Heads|XPZ|2.55"|Pacesetters|Stage 2 I/C. 12.442 @ 112.78
2000 Blue Bonneville SSEi Supercharged Gutted Airbox|K&N|3.4"|1.9'*|WP Pulley|Custom DHP|180*stat|41932'*|No Cat. 14.681 @ 94.80
2002 Dark Cherry Grand Prix GTP Supercharged & Intercooled
12.084 @ 114.38 w/1.743 60', 315.6whp, Fastest Stock Cam M90 GTP!
NOW XP CAMMED, 340.6whp with XP, stock heads, Gen 3 M90, 11.984 @ 115.84 w/1.750 60'!
Most HP Stock Heads Gen 3 M90 GTP!
2004 Red Monte SS Supercharged K&N|3.4 Pulley|1.9'*|180*stat|41919 plugs|3" dp|No cat/ubend|DHP|Shift Kit. 14.2 @ 98
GOT BOOST??? Friends dont let friends drive stock!