Lets say i am pulling up to a stop sign in 3rd and i am slowing down and put the clutch in to shift to first the idle drops to about 500/600 then goes back to normal at about 900. It happens when in max a/c. What do you think it is?

mods
licp,walbro,ams tbe hfc, turbotrix tune,kn drop in, hallman @22
334 awhp, 338tq

 

a/c is using a lot of the power