The butterfly is there primarily for the emissions systems (EGR), yes. Some folks like to think it is also to limit run-away situations if there is a injection system failure. Also it makes engine shut down a little less harsh (less air being compressed on engine shut down).Thanks, I've already taken off the egr system, so it's just there to cause vacume to suck in exhaust gasses?
Do take out both butterfly's or just the big one.
I did my 1KZTE on the truck... Just put a rag down the intake first to catch anything that falls....You'll need to drill out the screws that hold the butterfly in, because they have a permanent lock-tite compound on them and don't screw out.
That is strange about the engine braking, because with more air there is more compression, meaning it should be doing better at engine braking.When I did it on my KZJ71 I found that I lost a lot of engine braking and a lot rougher on shut down