tysir

i need some mad help here. i got my swap done 2 months ago and now the idle is tweaking. when i start the car, the idle is normal and stays at 800 to 900 rpm. i let the car warm up and still it stays 800 to 900 rpm, which is normal. BUT, when i drive the car normally, the idle drops all the way down to 400 to 500 rpm. anyone knows whats wrong with that. thats scares the hell out of me. i just dont want my car to die out. please if anyone can help me out.