The OS plugs are high quality plugs, however, they don't have the same taper for the turbo plug Nova engines, you can put one in there and it will work, but sometimes going back to an OD or Nova plug it can leak and make the engine stall. Sometimes not, but sometimes. I have found the OS plugs are good, but are a little hot and the thin wire burns out faster, esp, in hotter climates. the 97T is the best, no doubt about it...

If the p4 plug is cooler than the p3 then it should be better than a p3....and last longer...

Look at the coils of a 97t, then of a p3. Big difference, the 97t lasts longer because of the thickness of the wire, and they are half the price, win win...

Now in the winter or colder days the 87t would be just fine. If you live where it's mostly colder than 75 degrees then the 87t would be the ticket..

For the rest of us in hotter climates the 97t survives the burn....

For example in the winter in Texas, not really cold here, but it can be 50 degrees outside, and the engine needs a slightly hotter plug, a med hot usually, and the engine comes off the track at 230 degrees....keeps the idle up and steady....

In the summer. 90 plus temps, the cooler plug the 97t keeps lit all day long no matter what, and keeps the idle lower. the engine comes off at 250. That 20 degrees difference is why you change temps on the plug. The change isn't dramatic plug wise, you should never need a super hot plug, or extra hot or whatever, not should you need a dedicated cold plug..