hey guys, i have a rb20det swap in my 240sx and i just started noticing that when i stop and let it idle for 5 or so min. it starts sputtering and wanting to die?? i give it gas and rev it to 2k rpms and u can hear it sputtering in the exhaust. when i start moving i feels like somethings holding it back , then it lets go and runs fine???I havent had it tuned and its pretty much stock. so you guys have any one have and solutions???