Dude, if you ever run up on a full exhaust for a good price, get it. I had a setup similar to you, exup removed, graves slip ons, y-pipe. When I put on the graves headers, it was late and I couldn’t get in a test ride that night. The next day I though someone from yamaha came in the garage at night while I was sleeping and replaced the motor with a different one. I don’t know what the heck could be wrong with that stock header (besides having the exup cut your fun at 7k), but once I replaced them i picked up like 20hp at 7k, and a solid 7-10hp thru-out, before tuning.
Nice kill too.