I have a 2011 GTX LTD I/S with an 83 Nozzel. My impellar was sent to Speedfreek for the set back Mod and repitch 12.5/21.5. I have Riva air intake and SCOM installed. I am turning 7800 RPM's with 1/2 tank of fuel. Should I repitch my impellar if so what pitch or just add the 87 Nozzel to get to 8,000 RPM's?