On my old Tahoe and Avalanche, I used to clean the carbon from intake. I don't know what the H2 looks like under the hood (I have an H3; my H2 SUT is on order!
), but basically follow the black hose from the air filter box to the top of the engine. Unscrew the metal bracket the holds the hose on to the metal intake and look inside. You should see a flap-plate. Push either the top or bottom to open and look inside. You will probably see some black carbon buildup. Buy some injector spray cleaner (about 2 or 3 bucks at Autozone), put a paper towel under the intake on the outside and spray that cleaner on the inside wall while holding that little flap open. Then take another towel and gently clean where you just sprayed. Then put the hose and clamp back on and start your engine!
Your engine will be a little difficult to start at first, and might even cut out, but then she should fire right up. Just double check the instructions on the can.
Like I said, I used to do this about every 10,000 miles on my old Tahoe and Avalanche, and it really helped out. I would find that when the carbon would build up, the idle would be a little rough and the power seemed less when the air conditioner was on. I don't know about the H2 and might be way off base here, but it was a good tech tip on those vehicles.
Good luck!
Trinity