I tried the 6000 cfm from summit racing on my 03 dmax, went from los angeles to vegas last summer on 95-103F temp, the edge attitude temp indicated 134F on the big hill. only pulling 2 watercraft, had to turn the ac off for the engine not to over heat. tried different settings, no luck. returned the electric fan to summit racing when I got back, they're not too thrill about giving my money back. had to speak with the manager to settle.
actually the diesel runs couple hundred degree cooler than a gasser, on the exhaust side if it's the same configurations.