On my 6.0 with TR224, those same heads knocked about .5 off my 1/4mi time...
That really isn't too horrible as heavy as that pig is! Lol what was your time before the heads?
06 Intimidator SS- Tuned, CAI -DD
03 Silverado- Last incarnation 13.6... RIP
Ls1, Pnp heads, Polluter camshaft, spray, 4k stall on the way "Seize the day like you seize your noodle" - Shin Chan