hi there new to here quick question
 

hi there my uncle has a 2001 2500 5.9l, 150k on it no upgrades had since new. recently he has had these problems with when its cold out, it starts fine but when he starts to drive its seems to bog down it felt like to me it went into some limp mode. only does it when its cold untill its warms up weather wise it does it. when he is driving it and it does it and he turns the key off and back on it drives fine for about a min then does it again. he had it happen before when it was under warranty and the dealer took it in and fixed it and now that its over it warranty. they never told him what was wrong the first time and wont talk to him with out their shop rate clock ticking$$$ any ideas thanks