i would say the hesitation has to do with the way your car is tuned. its either a fuel problem or your timing isn't right. how is your car tuned? just the greddy e-manage or the "blue box" that is untunable? and does it studder at 4400 or 5800?

i have the greddy turbo on mine and my car boggs at 5800 because there is a flat spot. in two days, its getting tuned with uberdata and that will be gone. yours might be the same thing.

i wouldn't worry about the smell, i get it too.