I have concluded experimentally that my '05 Limited Couple was octane and air limited.

Replaced the air box with the MB V8 one with K&N filters, big improvement in throttle response, esp. at low to mid revs.

I'm in Phoenix, 91 octane premium sucks 'cuz of the air pollution-required stuff they do to it. By "splash blending" with 100 octane unleaded racing gas ($4.65 a gallon) I find that at 93 or so octane everything smoothes out remarkably - acceleration is continuous thru the rev range, sudden throttle openings at mid-revs are much smoother. Even my gf said something about how it felt, and when I had one of our race drivers drive it, he said I had made major improvements - thought I'd changed the computer !!!

I have now tried the 91 octane gas with 104OctaneBoost (one of the better octane boosters, and it didn't harm my Audi Sport Quattro or other German cars in extended use), and have the same results. BTW, I use either Techron or Shell gas here, seem to be the best and most consistent, not the cheap sh*t.

Tazz