The 924 was a great car for its day, but today..well today is greater than the 924.
Coming from 20 years of owning and driving a 924, here is my take on what you can do to try to bring the 924 into today's world.

 

Driving position and ergonomics recipe:

-Original 924/911 early sports seats
-90mm deep dish steering wheel
-wider pedals

 

Suspension setup recipe:

-26mm front sway bar
-18mm rear sway bar
-modern shocks (Bilstein, GAZ, KW)
-275Nmm front springs
-200Nmm rear springs (added to the existing torsion bars)
-complete set of polyurethane bushings 

 

Wheels and tires recipe:

-16" wheels for perfect balance of comfort vs stiffness
-all 4 tires must be identical
-Dont use economy tires, dont over-tire your 924, i use Toyo T1R 195/50/16. 

 

More power go quicker recipe:

-V3 supercharger kit from the924.com
-63mm exhaust
-proper fueling tune by permanent AFR monitoring system / dyno session
-fresh plugs, leads, cap, rotor
-drive the car hard once in a while, if you "diesel drive" it the plugs will foul with oil as these are old engines and they need to be driven not pampered.

 

bring her up from the dead quick recipe:

-electrics!! fuel pump needs to be able to draw full amps, otherwise your fueling will not be reliable.
-WUR and fuel dizzy, send them out to a specialized shop for rebuild
-new injectors
-new fuel pump and filter
-get the 924T or 944 brakes if possible, if not, everything new and proper
-DRIVE IT!