So I haven't been on in a while, business has picked up considerably for me. But it seems like the consensus on the forum is to go with the Flashpaq. I have an 06 4.7L, and it appears that several have already used these on their XK's. I don't care about performance or more go-fast feel. I tow a 24ft travel trailer (which is probably on the close side to being at the XK's tow limit) and need more umph...yes, I said umph...I can usually only muster about 55 without sending the revs to 3500 or higher. I don't mind running them higher when needing to pass or get going, but for optimal fuel mileage, 2k rpm is about perfect. When towing, I try to keep it about 2500 rpm. I average about 13.5 everyday driving, when towing it drops to about 9 mpgs. Not too bad, I guess....so...point of this long post is to ask for some advice...anybody?