I am running a N/A 14.1 comp 408 SBF and justed ran some C16 versus the C12. Seemed that the car slowed with the C16. Went 9.92 @ 135 with C12 and slowed to 10.11 @ 133 with C16. Can you guys give me some recomendations on what fuel I should be running and explain if and why too much octane would slow the car? Maybe something else slowed the car. Thank for any help.