I agree on it being twitchy, I tried mine in SP7 but I had trouble pulling away I either went or stalled
Yes it does work in all gears, the response in 4th or 5th is just as instant as the first 3, which I like because I'm not a traffic light dragster, just like a bit extra when overtaking etc.
Thinking about it more I had new clutch / flywheel done at abbey, then a couple of weeks later got plenum spacer & new exhaust fitted at abbey too, then got the D1 so maybe that's why I noticed the difference so much