Do phenolic spacers work???

[Blaster]

My dyno sheet was 251hp at 5700rpm and 270.5 ft/lbs at 4200, this is at 3500 ft above sea level and the air was kind of crappy. For reference I watched 2 stockish LS-1 vettes going at it that night at the strip and they were running 14.1 and 13.9 (I run mid to lower 13's ) . My car is a 91 loaded GT 5-speed without A/C. I have performer #6037 heads, e-cam, typhoon intake, 70mm t-body, ported stock mass air, stock injectors, 1 5/8" shorty headers, x-pipe, no cats, 40 series flowmasters, and 3.55's. Am I making good power factoring in my altitude?? (3500 or higher with bad air), the weight of the car was input at 3300lbs for the dyno but true weight with driver is about 3500lbs.