on a slope should be ok, depending what gradient the slope is. get the front end high, and if you can, chock the back wheels and then jack the front up a bit more
the hesitation on gear change could be down to the dump valve. try to get a standard recirc valve and see if that makes it better. quick lesson on fueling, the ECU monitors how much air enters the system with the MAF, the ECU adds the correct amount of fuel to that amount of air to give the ideal mix. - once air enters the system it is 'accounted for', so (with a dump valve fitted) on a gear change the air that has been accounted for get's dumped out of the system, then when in gear and back on the power (just for a split second) the mixture is rich, due to the air leaving the system and mixture being wrong
I have run scoobies with and without dump valves and I prefer the smoothness of the standard recirc valve