Keep it in there. It does actually work even on a race car. The fucntion of the ISV is to act as a form of choke during cold starts. So without one on a cold start you will have too low of an idle speed and the car won't idle. You can increase the idle speed to compensate, but then you get a high idle when warmed up.
Our rules are as follows
12 Induction / Exhaust / Fuel Systems/Engine Management
12.1 Throttle Body, Intake Manifold and Air Flow Meter
The throttle body and intake manifold must remain stock with no modifications. The air flow meter must be unmodified but can be adjusted (tuned).
12.2 Air Filter
Any air filter or filtration system may be used.
12.3 Ignition System
Any spark plugs and spark plug wires may be used. Offset woodruff keys are not allowed between camshaft and camshaft gear.
12.4 Fuel Filler Neck
Fuel filler restrictor must remain in the stock location.
12.5 Computer Engine Management System
The stock computer engine management system (DME) is required. Factory unmodified chips are required.
12.6 Fuel Delivery System
All components of the fuel delivery system must remain stock and unmodified, except for the addition of a fuel cell.
The sections above combine to say in effect stock stock stock with respect to entire engine managment system with a few exceptions.
The 944 engine is controlled with 3 elements. Air, Fuel and Spark.
Simple breakdown of the rules
What controls Air Intake Requirments
12.1 = Air Intake system must be stock (Including ISV for 85.5 fuel injection)
12.2 = Exception to 12.1 is anything before the AFM (ie air filter and cone filters are legal)
Controls Spark
12.3 = Stock ignition system, but you can use any plug or wire. Otherwise stock
12.5 = DME must be stock
Fuel
12.6 = All components must be stock but you can use a fuel cell
The ISV is part of the intake/throttle system (12.1) which is required to be stock. This also means the stock oil filler/breather system must remain stock as it is a major part of the intake system after the AFM.
I also want to add that the early cars 83-85 do not use an ISV, but they infact use to valves. One is a bimetallic valve used to contorl cold idle and this is under the intake manifold. The other is a valve used to control just the Idle with AC operation. This valve is located behind the stock airbox. In this case you may remove the second A/C valve as it functions only with A/C operation. The valve under the intake must remain. The ISV does both things, but must remain because it is part of standard intake air control section.
