Where did my .2 and 1.5 mph go?

[mplss]

Hey all-

I have a question about suspected power loss. I bracket race at rfr in Wisc., and the last two years in April, I made my 2 best ever passes. 13.086 @108.44 in april of '05, and 13.046 @108.77 in april of '06. This april, I cant get into the 13.teens, and my traps are around 106, the only difference being the addition of ngk-55I iridium plugs-does my car not like these plugs, or should I be thinking slipping clutch/bent pusrod, etc.? Any input would be greatly appreciated-sucks to lose ground.

[98ls1blackbird]

Its probably the air, if the atmospheric pressure was low and high humidity, it will kick the shit out of your performance. Ive seen two three tenths from mid summer to late fall. Try to find a racer with a weather station and find out the density altitude and keep track of the performance with different DA's.

[ImpalaSSpeed96]

So by 13.teens you mean 13.15 for example? Cause if you can't break 13's period, there's definitely a problem. Otherwise, weather can easily cause you to lose 2 tenths. It can even cause you to lose half a second.....