If I try to drive gently, freeway gas mileage can touch 16mpg at 65mph, but as soon as hills or traffic come up, it gets down to 13-14mpg. Around town it is more like 10mpg with stop and go waiting at traffic lights. Going up mountains with the trailer, 1-3mpg is common

Towing in general (flats and hills and mountains) works out to about 9mpg.
The Radix supercharger is bypassed for mild driving so it has little effect on mpg until the manifold vacuum drops and the supercharger starts whining sound (a lovely sound, if some what fuel-ishly expensive sound

) I don't know if the Paxton does the same bypass thing, although I would guess it does. As I recall the Paxton is a centrifugal supercharger which makes it's boost in the higher RPMs, vs the Radix which is a roots type and gives boost right off the line. But it has been a long time since I shopped that info.
Minor quibble between the Denali and the SS, according to what I find on the internet, in 2003 the Denali had the LQ4 6 liter 325hp and the SS had the LQ9 6 liter 345hp.
I have often wondered how it would be to have the all wheel steering. Would be handy in tight parking situations. But I hear it adds weight and complication to things
My engine is still running strong, but the paint is needing help. Clear coat is flaking off on the tops. I am saving up for a re-paint.