I've ran tri-y's on a bunch of high revvin' skinny block Fords, they sound great and work even better...... Only thing we ever found more (dyno) horsepower with on a high rpm engine was a set of Jere Stahl step headers.... To qualify this though, I haven't played header and dyno games for about 10 years so maybe the new headers work better, don't know. Not sure what the tri-y's do on a bigger engine, here I'm assuming you are running a 350?????