E85 is awesome. And it's good insurance so long as you're not using winter blend.
I'd be interested to see if their systems were direct port or using a plate. I trust TPI with a carb and using kits that are +500hp. To me, plates can be sketchy above that level. That's just my experience.
There are plenty of guys going 8s with nitrous and a carb. Tons. But I've been doing this long enough to know that big horsepower kills parts. EFI allows the mill to live longer because I'M telling it what I want it to do. I can manipulate almost every function with the touch of a button and data log everything. I can also program it to shutdown in the event of a lean condition or a knock to save itself. Traction and wheelie control. The benefits far outweigh the negatives.
Technology is our friend in this case. It just costs more and there's a learning curve.