hi everyone, i just perchased my first fd. its a 93 r1 with a bunch of reliability mods, radiator, downpipe, ect.....

so to my situation, when im coming to a stop and i push the clutch in, the car revs down to either 1900 or 1300 rpms. when i come to a complete stop, the cars rpms drop to 750 to 900ish. is that normal? the guy said there was a leak in the vaccumm lines some where because the turbos are really loud. when i idle, the boost gauge shows a vaccumm around of 17 to 19 at first then goes to 12. sometimes the cars rpms start to drop a little and then it jumps back up to 900. this is without a/c on. when i turn the a/c on, the car idles around 950. but if i let go of the brake pedal and press it again, the car will start to die and will stall if i dont give it some gas. sometimes the car stalls randomly when im waiting at the stop light with the a/c on 2. the guy i bought from just re-did the a/c because there was a leak. its r134 if that helps anything

i tried looking for the leak, but i cant hear anything. i did find one hose connected and one of the nipples plugged. i unplugged the nipple and connected the hose to it because it seemed like thats were it used to be. when it was connected, the car ran worse. so i plugged the nipple and left the hose unconnected.

since i just got it, im doing a complete tune up. im flushing the coolant, oil, changing the fuel filter, and new spark plugs. would the spark plugs or fuel filter have any effect?

anyone got any ideas what could be wrong?