mine shifts at 5500 unless i do it manually. the motor is good to 6500. if i shift at 55 it shifts at 6. works better for me but then i have a trany and motor built for it. no manual shift body though. i like to put it in drive when normal driving.

 

for a drag race there is not point unless you want to over rev past the set shift point. LS1 are set anywhere between around 5800-6100 depending on year and specific tune. (fund a stock ws6 tune vs my z28 tune, both 1999 cars but mine shifts at 5900 and the ws6 at 6000 ish). The only way I could see it being useful would be if shift at WOT is set incorrect, say at 3000 rpm, so he needs to 'maunally' do it to shift at peak power around the 5600 mark.

for a road race with turns and such it is better to do it manually, so that when you are on and off the throttle the car isn't gear hunting. If you slow down for a turn, in D it will upshift, but held in 2 it will hold gear so better when you get back on throttle

 

I'm not sure how good that is for the trans, but it has a valid purpose driving in the winter for better control and acceleration. Doing this is similar to the 5th Gen Camaro automatic with the tap-shift -- you get some of the control of a manual w/out clutch...

 

putting it into D3 makes it not upshift once it gets into 3rd gear. putting it in D2 makes it not upshift once you get into 2nd. its sole purpose is for road conditions, such as hills. it was not made to make the car a high performance race king

 

haha race king i like I'll call him that from now on