My 2002 tahoe has 213,*** miles on it. I bought it back when it had 165k and it hasn't given me any trouble. Doesn't use any oil or smoke and still has power. I paid 7k for it with that many miles though.
I have 40 series flowmaster, intake, and a tune and i get 19 on highway with the weight. I got 17 when i had 24's on it with the system. I know thats not alot but for everything i got in it and the size i dont see it being bad.