I am a farely new diesel owner. I just purchased a 06' 6.0 with qpprox 70k miles. I am going to keep it stock for a while until I due the proper upgrades, (egr, head studs, etc.) before I think about tuner. I just purchased cat-delete and muff-delete pipes and was wondering if this is ok for the time being? Should I go turbo back 4" cat-delete now, or wait until tune? Possibly cat back with the cat-delete pipe and buy the down pipe later? Is bigger than stock pipe nescessary with no tune? Thanks for the help!