When I cold start my 1996 Mach-Z. I use full choke it takes 3-4 pulls to start. Then I quickly go to 1/2 choke for a short time, then no choke. Total warm up time maybe one miniute. I try to start real easy until engine warms up. I,ve had some slight poping or backfiring when starting out, when engine warms up it runs reel good. My plugs look good, I'm runing 10's gaped at .020. I had 9's in it and it did not backfire. The 9's looked hot, but they were gaped to .030. Any ideas? The manual says to use 10's, but my fuel is only 90 oct. I can get 100LL and blend 50/50 or 40/60 and see what that does.