87bucketgta

Hey guys, I need some help/advice. I just got my throttle body back I had it sent off and rebuilt and bored to 52mm. My car always had a crazy kinda idle. I went ahead and also installed a new IAC while I was there. I followed the reset pro. and set the tps. And also set the timing. The problem I seem to be having now is car seems to Idle fine only thing is when Im setting base idle is says get it to about 450rpm, well I cant get it that low about 600 is as low as i can get it and it still runs. When I plug everything back in car idles really nice around 600-700 when I put it in gear it will die out almost everytime if I tap the gas and its fine till and will stay running. I go back to park and try to go to reverse or drive same thing again. Any advice!!! Thanks in advance