The 3/4" drive IR I got used had the bottom vent plastic cut out and the exhaust muffler removed already, so I don't have a reference to know how big of a difference it makes.
I can tell you, after rebuilding a LOT of air tools, the exhaust muffler material in some of them is pretty thick, and gets worse the more oil and dirt gets packed into it over time. Any air tool will work better the faster the air going in can get out of the exhaust.
Worst case, if you're not happy with it, sell it and pick up an IR 2145, I love mine. Or if you want an older model great working 2131, I have one for sale (it may not be pretty, but stick a boot on it and no one will ever know, haha

).