I did a tune up on my car, I didn't really expect it to run any better at the track seeing as the old stuff was fine(just wanted a new vacuum advance distributor and nice lookign wire looms) and I lost about 2 mph on the top end(98.12 was my best and afterwards could only get 96.Xs with best of 96.8).

Humidity was the same but the 2nd time out it was 15-20 degrees hotter. Would the tempature effect my car in such a way or should I be looking at the things I changed as a possible culprit(I changed to NGK v-power plugs from Ac Delcos cause they are shorter and don't hit headers). So does this loss seem possible with only the tempature change?

 

Yep. I've seen it happen in every car I've owned.

 

Weather can definelty make a differance in your ET, but you said you put a whole new distributor in. It is possible that the advance curve is different so if you cant seem to get that 2 mph back it may be in the timing.

 

Weather conditions should always de used to calculate a density altitude. Humidity, barometric pressure and temperature all contribute to a final result as well as the altitude of the track.

Humidity being the same doesn't mean anything. There's a lot more moisture in 80* air at 50% humidity than there is in 60* air at 50% humidity because of the higher saturation pressure.

Hot temperature also mean thinner air (less oxygen molecules per cubic foot of air). Less oxygen to burn equals less HP.

Barometric pressure plays a big part in the formula also. High pressure is better. That's what power adders do.

Chances are the changes you did helped but the poor conditions made it look bad. It's possible that without the changes you would have run even slower.