Looking to buy a tune

I Have an EFILive box and I have only tuned gas and I dont want to even attempt to tune a diesel as they are 5x more than a gas engine if I make a mistake. I have a friend with an 09 LMM and he wants a tune. He is willing to buy one and buy a license so I can flash it for him. My question is where is the best place to purchase a tune that I can flash in for him. He mentioned something about buying a DSP5 switch also so I assume he will be looking for that tune. Thanks in advance.

I've been using these guys for several dmax tunes.
Great guys to deal with so far.
Have done single tunes, DSP2, and DSP5 tunes with them.

http://duramaxtuner.com

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I am planning to get a tuner as well but a friend of mine recommended that I should try diablosport for my pickup.