Unless you have an older AC compressor like I used to, which didnt spin all that well, then it could help to get the belt. For me my compressor didnt turn all that freely, but it was still giving me cold air so for me it was worth it to buy a bypass belt for the track rather than replace the compressor. My belt would bypass smog, and AC but only for the track. That combined with removing excess weight: spare tire, jack, rear seats, passenger seat, mats, etc loose stuff seemed to improve my track times (by how much I cant say, I used to have pretty erratic times back then)...