2001 1500HD Crew 6.0L Pinging/knocking

I have a 2001 1500hd Crew 6.0L. It has 57k miles, 3.73 axle, dual flowmaster exhaust, and a K & N filter(not the mod, just the filter). I bought it last yr used, and I love it, but......

I have learned a lot on this forum from all you pros out there and I am looking for answers/advice on the following:

1. My 6.0l has less acceleration from a standstill than my 5.3L, 3.73 axle Suburban. Why? Is it because of the dual exhaust reducing the backpressure and lowering torque?
Different gearing in the tranny maybe? I bought the truck to replace the Burb for towing my 7000 lb RV, but it seems the burb does just as well without using as much gas.

2. It pings like a son of a gun when I punch it, especially after it is warmed up. It is better when it is still cold.
I took it in and nothing was found out of the ordinary, no codes, o2 , knock sensors good etc...
Do I just need to buy the premium gas?

Solutions I am looking at are:
-installing the full FIPK. Will that bring back my low end torque?
-reprogramming the chip/new chip
-bringing it to a GM dealer to get the PCM reflashed with the latest and greatest update. Is that worth the $80??

Am I missing something? I'm just not getting the mileage others are posting, nor the power I think I shoud be getting from this 6.0. Any ideas would be appreciated. Thanks.