hi did ls swap 5.3 with 4l60e little hard to start sometimes have to hit gas pedal while cranking when starts idles around 800-1000 rpm put it in gear let off brake starts to move under idle then idle drops to 400-500 sometimes almost stalling give it gas drives ok then when coming to a stop it idles down almost stalling out but once u stop after about 10-12 seconds it will idle up to a 1000 rpm but as soon as u let off the gas it starts to move under idle then in about 15-20 seconds it drops back down to 400-500 rpm almost stalling out any help is appreciated thanks