I'm thinking of selling my 02 and getting a SD. How are the 6.0 diesel motors for reliability and maint. Are you guys having any real issues that seem to be common with these. How much can you reasonably crank them up with a tune vs a kit like Bully Dog, Gale Banks, etc. Any insight you guys can shed would be cool. Oh, I'l be buying used probably 04-06. Any years there to avoid?