I just bought a 2007 Tahoe Q6 with the 4.3 Liter MPI motor. I took a test ride on it before buying and there was significant porpoising and the trim was overly touchy. I bought it and before I took it out I installed smart tabs and changed out the 14.25x21 aluminum prop with a 14x20 Alpha 4 aluminum prop. It now performs SIGNIFICANTLY better! No porpoising and planes almost immediately. I was able to run it WOT today with GPS and got 44 MPH with 4300 RPM. I downloaded a GPS on my iPhone for the speed. The rpm's were per the gauge on the boat. I'm more concerned with hole shot than I am with top end speed. Since the recommended RPM's for this motor are 4400-4800 RPM, would it benefit me to go to a revolution 4 stainless steel in 19 pitch or am I pretty close to perfect right now? That's a whole lot of money to spend for a minimal improvement in performance. But, you all are the experts. Let me know what you think. Thanks!