Hello I have a 2004 Mustang v6 first start of the day it runs great although I feel a horrible vibration through the car when I put it in drive but it goes away fast then runs great. If I turn it of for 20m then start, it idles horrible gets worse under load then gets better after raising the rpms, I replaced the spark plugs and the spark plug wires along with iac and egr, I'm breaking it down to my exhaust leak, coils, fuel injectors whitch is more likely to cause this