I got the DISTRIBUTOR type for my MKIII NA. Your MKIV uses a distributor also, so I would guess you need the D type. Check with SupraStore.com or SupraSport.com
Just curious where you plug in the harness for the DLI. Your picture shows it on the passenger side but aren't the connectors with the ignition wiring on the driver's side? Is the plug and play harness made by HKS and how much does it cost (hopefully less than the silly price they are charging for a VPC harness).
where you plug in the harness for the DLI?
You plug it in on the passenger side. it is between the coil and the distributor.
Is the plug and play harness made by HKS and how much does it cost?
Yes it is an HKS piece, and costs somewhere around $40
what exactly do these ignition systems do? Anything for performance?
The Twin power amplifies the spark. this is so you get a more efficient burn. Less likely to detonate.
Does Improve performance as far as a HP number i dont have one, but the more important thing is that it makes your car more efficient.