i need some advice. my 97 integra has an ls/vtec swap, exhaust, headers, intake and intake mani. the problem is when i slow to stop, and i put it in neutral the idle goes from about a grand to 2-500 rpms. SOMETIMES (its pretty rare for it to happen, but it has done this), it pulses and the oil pressure lights for a second and goes of and this process repeats until i throw it into 1st and accelerate. the car drives fine actually, except for this idling problem. Any advice?

also noted the antifreeze and the oil were recently changed.

thanks