little smathers

hello everyone, I have a 2000 model and i have bored .020 over put stroker crank and rods, rv cam .050 lift, tuned header, new head which is ported i can get port sizes if needed, ported and polished intake with a 70mm opening and throttlebbody, cold air intake, 2.5 ss catylic converter and monster cat back exhaust. i put all this together and fired it up run like a champ for 700 miles then as i was on the interstate traveling up a 6% grade with a 2000 ft. elevation change. #4 piston melted the skirt metal on the side that the injector sprays, and started a little bit on all other cyclinders. and made a heck of a noise. so i slowed down and then decided to press on. drove another hour at 75mph to the house. removed motor and found this. looks like to me it was running lean white spark plugs very little carbon build up on piston and inside header. one would think that it ran rich and washed the cylinder and then when i let off gas computer changed set up and no more problem. do i need to look at getting a bigger map sensor for the extra air flow or does anyone have any ideas. i think i may need a adjustable fuel regulator also 46psi needs to 49 for the 24lb injectors that are in it. i bought my entire kit from rpm machine in idaho seemed to be good things, great help!