That's impressive! I hadn't seen that build of his. I thought the Engine Power 350 was pretty weak with all the trick parts they used, but it's been years since I've seen the episode and I bet CutlassEFI would've spec'd a way better cam than some off the shelf Comp or Edelbrock Performer unit they selected.
I bet the reason the Gen 5 felt so much stronger than the Gen 3 is because the Gen 5 has Variable Cam timing (the Gen 4s do as well). The Gen 5 is definitely superior in a power production standpoint as well but Variable Cam timing really helps maximize the low speed torque and high RPM power, that's probably the single greatest factor affecting driving feel. The only real problem with the Gen 4 & 5 is AFM issues which can be as minor as heavy oil burning or worst case failed lifters.
I used EFILive and a dongle USB to OBDII to collect data on my laptop and then sent that off to
Blackbear tuning (they will loan you a dongle) and they developed the tune for my truck, but a Dyno Session with an experienced GM tuner would be even better. It made my truck feel like a completely different truck and with the
Shift Improvement kit I have no complaints with how my truck drives, (even just a corvette servo and no tuning or shift kit can really help firm up shifts in the 4L60e, I actually had to pull it out of mine after the shift kit and increased line pressures of the tune caused it'd bark the tires on the 1/2 and 2/3 upshifts) it has instant downshifts and any part throttle hesitation that it had before the tune is gone. I was honestly about ready to sell my truck before the tune because I thought it was such a dog after driving some newer trucks, it didn't bring it up to level of a 6.2 in a Denali or Escalade but it was the best $350 I've spent on the truck by far and saved me thousands by not buying a newer truck.