First Mods? Where to start....

So you have a TBSS but not sure where to start when it comes to adding aftermarket performance parts? Below are the most common upgrades. At this point I can personally vouch for 90% of the below as being fact. Most of these pro's/con's are the general consensus on the forums.

Increased Performance often including better mileage, better all around drivability including improved transmission shifting. Requires sending modules in to be programmed, getting an extra set of modules that are already pre programmed or flashing the tune yourself using HPTuners or EFI Live software. More info None

Increased performance when used with above "tune". Better flow because stock neckdown is usually removed. Looks better than stock intake and truck makes more engine noise because stock baffles are removed.

More info here
If used without a tune the truck will run leaner reducing performance and often throwing lean check engine codes. There is NO reason to install an intake without a tune. There are no other con's.
Intakes "CAI"

Increased performance because of less drag on engine. Usually quieter than stock. Increased space in engine bay to work on front of engine components and increased space to run custom intake systems

More info here
None but requires custom ECM programming to clear check engine light and make electric fan(s) function.
Electric Fans

Increased horsepower because the water pump, alternator, AC, power steering, etc are not being spun as fast thus wasting power. Requires new main belt and new AC belt

More info here
Possible less charging at idle with alternator.
You can add a overdrive pulley to the alternator to offset this. I am running a underdrive pulley and even with a 500 watt amplifier in the truck I have no issues.
UD Pulley

Greatly increase performance (usually .5 second in quarter mile) Often cuts 3 to 5 tenths off 60' time

More info here
Depending on size of stall, decreased mileage, decreased drivability, increased stress on transmission and increased fluid temps meaning aftermarket transmission cooler is required. Highly recommend upgrading transmission before adding a stall converter.Tune highly recommended. Possible speedo and towing issues. More info here
Stall Converter

Often Sounds better. Sometimes worse. Usually no performance gains on the TBSS even though often advertised with gains. Many catback systems exhibit annoying drone at certain speeds.
Catback Exhaust

An upgraded transmission improves shifting and drivability. But most importantly it replaces the stock weak transmission. A must for anyone that plans on any serious modifications. Note: AWD trucks are more prone to failures than 2WD trucks. None
Upgraded Transmission

Increased performance which usually shows up as you add mods to the truck like cams and power adders. The gain on a lightly modded vehicle is not as great as some other vehicles.
Better throttle response and pulls harder on top end. Good mod but low bang/buck.
Tune will often need AFR adjusted because of flow change. Tune highly recommended.

Cooler transmission temps with increased transmission longevity. This is a required option for anyone using a stall converter and is a good idea for anyone towing. None
Transmission Cooler
Firmer shifts by applying more pressure to the apply pin which creates less slippage on the drum during the shift. Choosing the wrong servo in combination with shift kit and/or tuning can create an excessively hard shift resulting in potential breakage of hard parts. The Corvette 1-2 servo seems to be the best choice and is used by top builders. Using the stronger billet 4th gear servo seems to be acceptable.
Transmission Servos