[legion]

I've put Bosch Platinum 4's in three of my cars.

The car will run much better...initially.

Anywhere between 3 months and 3 years, the car will start misfiring.

I had the same question (in the Turbo forum). I've done some research, and just yesterday one of my former cars (which I sold to a friend) was misfiring because of the Platinum +4's I installed 3 years ago. I put some Platinum 2's in the F150, and it has been running rough ever since (I plan on changing them tonight).