I just went to get my oil changed,2 new back tires, and to have my A/C recharged.. When I got in my car after all the work was done, the car was idling around 2000 rpm, after taking it down the road, it quit doing that and the idle is at 800 now, but when I turn the car off,as the boost gauge is going back down to 0, it makes a loud boat horn like sound for about 1 second from right around the airbox. I haven't had a chance to check around the area yet, because i had all the work done on my break...Just curious to see if anyone else had any kind of problem like this before and what caused it..Thanks Guys....By the way my car is a 90 5 speed SC