I tow my 8000lbs with an '07 3-valve 5.4, and while it does it ok, it needs to spin quite often to get it done. I don't mind being down on power most of the time, but one of the times I do mind it is certain entrance ramps where you don't have the power to get up to speed with traffic. Then you're at the end of the ramp, with the pedal mashed into the carpet, having timed it as best you can, and you're counting on someone's kindness to let you in. You almost have no choice but to go for it and take the spot sometimes, because jamming on the binders at the moment of truth isn't a good idea either. I wouldn't want to tow any heavier, that's for sure.