Ideal Heated Knives [IHK]
No web site listed
Heated tire groovers and accessories

IDIDIT Inc. [IDI]
http://www.ididitinc.com/
Steering columns and accessories

Impact Racing [IMP]
http://www.impactraceproducts.com/
Helmets and safety equipment

Inglese Induction [ING]
http://www.inglese.com/
Weber induction systems

Innovate Motorsports [INN]
http://www.innovatemotorsports.com/
Electronic Engine Tuning Tools and Accessories

Insulator [INS]
http://www.bondedlogic.com/
Under hood and interior insulation

Intercomp [INT]
http://www.intercomp-racing.com/
Racing scales and equipment

Isky Cams [ISK]
http://www.iskycams.com/
Performance cams and accessories