I was visiting the SLP web site, watching the 10-spoke wheels, and came across this item on clearance:
Torque Converter, Lock-Up 1997-05 W-Body (4T65E/3000 Stall)
Price: REGULARLY $549.00 NOW $399.95

My question is, why is changing the torque converter of benefit?

Probably has something to do with it spinning up faster.

?

Basically will give you harder launches. Puts your engine in the power band right away. Also probably lighter weight than stock, so perhaps a few freed up horsies?

Generally the more aggressive you get on the cam the higher stall converter you need.

Do a google on torque converters operations and you'll see why people would need a higher stall torque converter. For most of us with little to no mods a higher stall torque converter will hurt the perfomance of our cars and eat alot more fuel as well.