That's definitely running lean. So you confirm you are running 12 degrees initial base timing? What's your fuel pressure set at? You are running 19# injectors and a matched MAF?
Do you have pictures of the engine? Just want to see if something jumps out as being incorrect
Just thought I'd share with the rest of the gang a PM this ASSHAT who doesn't know a spark plug from a butt plug sent me the other day. He PM'd me about this problem and apparently didn't approve of my answer of posting his question on the board to get more responses in addition to checking his timing and using a laser heat gun to check temps at the intake, exhaust, valve covers, radiator, etc.
" Monday at 6:28 PM I am having trouble with the 5.0 I just put in the 91 fox GT. Headers were hot after 20 sec of running, after that I set the timing, checked all vacuum, cleaned IAC, the idle dropped down to 1,000 rpm which is better then 2500, the headers still get red hot but it takes about 5 min to get red, also valve covers are hotter then they should be and the plenum gets hot to the touch, the motor came with a 97 explorer intake and plenum, I'm using stock TB.
"If your valve covers get hot enough to melt the skin off your finger then getting a f***ing heat gun to confirm they are to hot is something a friggin idiot would do, what good is having the actual temp if u know it's obviously to hot. Why are you even on the forums, nvm ill ask someone else."