DO you have a super charger or NOS? The +4 has no ground strap(on top of the electrode) to Glow and if you have not Indexed the plug so that the ground strap is not Blocking the spark facing the intake valve you will lose some HP. . But running a colder plug only helps in keeping the pistion temp down a bit for wide open racing for long period of times. It is your choice but if you have not used a product how can you really know the difference. My point is about the newer C4's with the LT1/LT4 and that AC spark plug does not last(disc's burning off and falling in the cylinder) like GM said. Read my earlier post again. The AC plug you use is a good plug for the L98 but how many miles does it last? The +4 design will produce a hotter spark and last longer as I have 58,000 miles on the set in my wifes 94 TA LT1 that is driven to work every day(stop and go heavy traffic) 58 miles each way and it still gets the same gas mileage after two years and it never needs a regular Blast to clean the plug..And look at the +4 again the Four ground straps are not Thin. And the Air Craft engines do use a Turbo Charger.