So I have now installed and tested my 2010 Cummins 3500.
I have learned lots but still have questions.
I have seen gains but not as much as I would like.

I installed a dry cell on my truck when it had 83,000 km on it. But in order to do this I have had to spend a fair amount of coin. I Installed a S&B CAI, DPF delete and a H&S mini max chip to start. I saw gains right off the start by doing this as expected. With the stock truck I averaged over a year 17 MPG (calculated) with peaks of 21 MPG over a tank of fuel and lows of 13 MPG while towing.
This was great as my old truck a 2006 F-350 6.0 averaged 14 MPG with lows of 8 MPG towing and highs of 16 MPG.

So now with a better platform to do mods on after i had installed the above parts I was averaging 20 MPG on a mild tune with agressive turbo tuning. I was excited with the gains.

I then installed a D-7 HHO cell from http://www.hydrogen-generators-usa.c...rogen_kit.html and did a lot of research about HHO

1)HHO is fast burning so retarding the timing is needed. Not a problem with the H&S chip this can be done.
2)In order to gain MPG you need to run lean. Not a problem with the agressive turbo tuning you force extra air into the engine
3)HHO being induced into an engine with multiple shot injectors the HHO gets burned up before the main fuel burst is injected into the cylender. PROBLEM
4)You cannot control the flow of HHO easily with different engine loads

I am still tunning my system and have tried different combinations but all I can get is 23.9 MPG (15% gain) from it. I have set my system to 30 amps @ 2.5 LPM but get horrible driveabilty issues like preignition and low power off idle. Currently I am running it very low @ 4.5 amps +/- 0.4 LPM and it runs better but still not perfect. I still get MPG gains but it idles rough (loops) about 50 rpm. It also seems to lag alittle at this setting with bursts of HP and power under certain loads almost like nitrous.

I do belive the potential is there to get 50% MPG gains like the website says but to get it right is another story. I will continue to tune my HHO system and keep you posted