engine idling

I just installed a Jeggs engine in my 98 tahoe 2wd. Checked all fluids good, Cranked over 2nd try it started up and went into a very high rpm. Shut it down. Tried again couple minutes later, same thing starts and it's like your foot is on the accelator flooring it. shut it down again. would this...

So, I've got an 2002 chevy Tahoe with a sixth cylinder misfire ONLY when it's idling for a while. I've replaced sixth cylinder coil pack, all spark plugs and Spark plug wires. Next I plan on changing fuel injectors. If anyone has any other ideas please let me know! Thx