I do not know if this was cured with the Tow Haul switch. But the 454 with 4l80e is very good but there was no way to keep torque converter locked at highway speeds. The 93 K 2500 I had was great but would lock and unlock on rolling hills on the highway so good cooling was needed, The tow haul mode stared in 96 with the Vortec I think. I would get an 8.1 if you can. The TBI's pre 96 like the 93 I had were dogs unless you installed headers free flowing exhaust and intake, Chip and bored throttle body woke them up pretty nice.
