Is your truck an early 99 or late 99?
Your EGT's concern me for being a stock truck but you do have a bigazz dually. Still with stock programming it should be hard to see 1200...
Your boost I hope is wrong, but that might be what is causing your high egt's. Definitely check for kinks in the boost line... I have done both AIH and map sensor plug in for boost - both after installing a chip go up to 25-28 so it shouldn't matter.