Well i swapped in the 3 in Mac cat-back about 2 weeks ago and put on the 2.75 ultra-grip in place of the 2.80. My best with the 2 1/2 and 2.80 was 458.6HP and 512LB-FT SAE. The outside temp that day was 67 degrees. I also sprayed a lil giggle gas(39 jet) after that run and netted a 515HP and 537LB-FT and that was spraying at 4500 rpms. A/F's stayed around 12-1 w/ a spot between 4000-5200 rpms going off the charts rich on both the NOS and Regular runs. Now the results, Temperature today at dyno time was 91 degrees. 442HP and 475LB-FT SAE only pull made off the bottle. Engine temp was at 188 degrees. Now i wanted to see what the larger 46 jet would yield. 512HP and 550LB-FT, he let off at 5500 because the A/F was starting to go lean. I put the 39 jet back in and ran again. 490HP and 552LB-FT and A/Fs were the same as before. steady around 12-1 going off the charts rich between 4000-5200. Im not disappointed at all considering the temp today. Only ting that concerns me is that Power starts falling off at 5500 whereas before power would not fall off until 6000. ???? Any ideas or suggestions?? Thanks for the space Jamie