I had an early 2004 F250 2 valve V10. I looked at most of the options for increased power but I never saw any performance charts for the Y-pipe only. Most of the comparisons and claims were for: chip + intake + y-pipe + exhaust. I could not get to where I wanted to be with that truck. Am now driving a 6.7 TD.
All of the above mods add power in the 3000+ RPM range. You normally don't tow in that RPM range except on hills. Is it worth the time and effort?
There are several posts on the performance forums about exhaust system resonance at certain RPMs with the Y-pipe mod, most of them with aftermarket exhausts.
If your objective is more power for towing then changing to a 4.30 gear set will serve you better. You will lose 1-2 mpg. Adding a Gear Venders Under/Overdrive will recover that lost mpg: https://www.gearvendors.com/