A leak down test would be good, I also think a compression check would tell you a lot. Even better if you could compare it to others!
What's the maximum RPM you're turning, and how does it compare to others, and what's the stall RPM on the clutch??
Where are you getting beat; through the corners, out of the corners, down the straight??
What fuel are you using? Is it controlled by the rules?
What are your weight percentages, front left cross?
What stagger in the rear?
What tire treatment are you using?
Just to show you that; "tuning is tough" (Al Nunley)