I have a '92 240SE which has started to idle very erratically of late.With the aircon on,it idles around 700rpm but if I switch off the air con,it gets worse-around 500rpm.The vacuum gauge climbs up to the red line when the car idle's but drops when the accelerator is pressed. BTW, my car is a Malaysian model, B230E with CIS mechanical fuel injection and manual gearbox.The fuel consumption has gone up a bit but not drastically though and the car tends to have flatspots if the rpm drops to around 1500 while driving.Anyone got any idea whats wrong with my car?Plugs are new,fuel filter was changed and the car was okay for a while but the problem returned after a couple of hours.Tried adding some tablets to the fuel tank which are suppose to clean the injectors but there's no difference.Once on the go,it runs okay.