Anyone use open header at the Track

I have usually run open headers, unbolt extension and exhaust pipe and bolt them up offset for drag racing. That leaves open header. This weekend for first time at track this year, I took pipes off extension and bolted extensions back onto headers. The car used to run 8.05 and 90 mph. Car picked up 8 mph, ran 99 mph all weekend. ET was 7.95 to 8.05 depending on heat and weather. I did a minor jet change and fresh plugs so I don't know what caused higher speed. Exhaust extensions or tune up?