The 5.0 in my 66 with Ford "suit case" injection surges below a 1500 idle. So far I've checked for vacuum leaks and found none, replaced the idle air control valve, the MAF and the Throttle Position Sensor with no results. I know this is an early Mustang forum, but I thought I'd give the question a try here because of the extensive mechanical knowledge among forum members. Because of this problem, I'm seriously thinking about going back to a carb. Thanks for any advice.