sr20det starts rough when its cold

[sr20_powerd]

so i drove my car about 100 miles then stayd the night at my buddys, got up then next morning and dyno'd my car (rev'd over 7500rpm) and drove it home. woke up the following day and drove it about 80 miles to my uncles and it ran fine, drove it home that day and it was fine. got up the next day and it starts really rough when its cold and is backfiring above 5krpm . its never done this before and ive had the engine swap for 4 years now. i did turn the fuel up to 40 psi at idol for the last run on the dyno and diddnt turn it back down till monday morning. any chance of valve float? or fouled plugs? dirty MAF?? any suggestions on what to check first would be helpfull. thankstrav

[r3v_v3ng3]

are they colder plugs?