Ok, so I already did a minor mod... Not really sure if it would be considered a mod though.
So I drilled out the stinger to make it a tad bigger. Off the line, this thing is killer. No glitches, no bog/stall/any of that. With the right tune, it's very good off the line.
However, top end dropped a little bit. Not sure if it was because of the transition from yellow to red pinion (HPI) or just the feel/look of it when acceleration kicked into top speed gear.

Tomorrow, I'm going to take apart the engine because I have nothing better to do... I stripped the second gear (modified chassis) and I'm going to need a new spur and chassis anyway.