I have 175/75's and my turbo cleans them up very well and that was with a factory manifold. For what's it worth, the cost for the upgraded nozzle is generally going to be the same whether you go 30% or 70%. You could opt for a Barder Stage 2, a set of 175/75's and have a fun performance truck and get a nice tow tune by a reputable writer and still have a functioning tow vehicle. If you really want to move some air and are up for a few extra dollars to spend, invest in a ported manifold and that will aid in keeping the egt's in check but again, good tuning will help as well.