I'm curious, have you tried airing down your tires yet and did it help or hurt your ET?
I have the exact same tire/wheel set-up as you, I dropped the tire pressure from 45 to 30 and noticed a drop in my 60' and 1/8 mile ET. Raised tire pressure back to 45 and picked back up on 60' and 1/8 ET.
2015 LML - Stock Turbo and Injectors, Built Tranny, Sportsman CP3
Dyno'd 2/6/16: 569 RWHP/1149 RWTQ
Best 1/8 mile: 8.20 sec
Best 1/4 mile: 12.98 sec
07.5 LMM (Previous truck)
Dyno'd 4/13/13: 643 RWHP/1086 RWTQ
Thanks to A-Star Diesel Performance (George Loewen)