Jetting for race gas

I need some jetting info for running half race gas and half pump gas. I started out with a stock 03 yz 250 and one size richer main jet (180, stock is 178) to compensate for cooler weather here in Kansas,the bike ran great. I then put on a PC Pipe and silencer and one size bigger main again(182).With the pipe on it started to ping in early midrange (with the 182) so I tried some VP C-12 and mixed it 50/50 with pump gas to help fight the pinging .It solved the pinging problem and ran okay but seemed a little sluggish in throttle response.Can I safely come back down to the (180main) or should I leave it alone.Temperature for riding days has been between 60 and 70 degrees.Thanks

Jetting was spot on with stock pipe as are all yz`s. I`m just wondering where I need to go with the addition of the pipe and race gas. I`ll probably try to go back to the 180 main and see what happens.