What are your power goals? Truck goals?
If you don't plan on much more than maybe adding a little fuel the StreetMaxR will get great.
If you plan on future larger injectors, dual pumps,built engine, 700+ hp etc... Go with the 6670R.
I'm not looking for a drag truck or anything, but want a good little hp/tq boost and a good sound. If I end up keeping stock fueling and just custom tuned & *****ed, would 6670R perform great? I have heard they have the old 6.0 whistle and I'm a former 6.0 guy that misses the diesel truck sounds... Or would you think the street max R is better? I know you have tested the 6670R for a year and I'm interested in what you think the comparison stock fueled is?
Also do you have and stock fueled 2015 videos of both turbos?