I think part of the reason the throttle seems so sluggish is how far down the pedal is to start with. It seemed terrible to me at first, but once I bent a bit of aluminium I had laying around and used a couple of leftover bolts to make a wedge bracket to bring the pedal up, (I used a spacer & some zip ties on the cable in my TJ), it was all good!
And, being a manual, I can heel & toe properly now!