Ideas for 215k truck

[porteri@email.sc.edu]

Hey guys I just got back my 2004 250 crew cab from my father (after getting rid of my '08 350 6.4 which was nothing but issues) and it now has 215,000 miles on it. All I did before he took it over was install a Banks cold air intake. Never had any issues with injectors, etc and never done any major maintenance on it either. I'm just looking for some ideas on what to do to improve the performance (and maybe some mpgs as I'm only at 11-13 now, riding on 35's) without hurting the truck due to the miles, as well as any big maintenance things I should take care of at this point. Thanks.