General LSX Automobile Discussion - lq4 silverado low end torque issue

i swapped my 4.8 dbw out of my 04 silverado and put in a 01 lq4 6.0.

the only parts swapped were the long block and coil rails and coils.

the intake and injector rails are all 4.8L

dont get my wrong this truck is rediculously fast now after having engine power systems program it but i have a couple issues i cant figure out.

lets say i try to do a powerbrake burnout, the tires break loose and the rpms climb slowly till about 4k or so then WAM rev limiter (6800rpm) and shift then the rpms are below 4k again and it starts bogging down again.

so idle to 4k = 5 or 6 seconds
4k to 6800 = half a second or so

the other issue is on idle in gear like sitting at a redlight there is a missfire that brings the idle rpm down to about 300, nearly stalls out. it is not consistant. every few seconds or so. and sometimes it doesnt do it at all.

the engine is pure stock, even all the external is stock.

might the first issue with only high end torque be the 4.8L intake?
that issue is deff consistant.

going 50 down the highway and i nail it, it breaks both rear tires loose and fishtails as it downshifts and the rpm's hit over 4k

going 60-70 and it downshifts when i nail it it is much slower because it only downshifts to 3rd and the rpms start off at about 3k. then it gets to 4k after a few seconds and im glued to the seat again.

i am running cat converters. and retained the rear o2 sens.

one more thing, its getting nearly 25-30 mpg on the highway when i use cruise.

im pretty dumbfounded on that one. make a round trip to jackson MS from meridian MS on 1/8th tank of gas.

edit* also the engine has had this tack tack tack sound coming from the timing chain cover since the first time i cranked it up that only goes away when i add that blue engine restorer stuff and after about 500 miles it starts back up.