Just had an expensive lesson. on the first service, 4000 miles I gave the mechanic the brisk plugs to install, he said are you sure? I said yes as I had used them in both the X10350 and the 500. What a mistake just cost me £45 to have NGK's put back. The burg with the brisk lost power at critical times i.e. when going to overtake, the engine braking was interrmittent (sometimes felling it was going to cut out and no engine braking). I thought it was the breather pipe on the fuel tank as I thought it was fuel starvation caused by a vacuum. To my surprise returning to NGK's returned the burg back to its former self + a littel more. The moral is beware the Brisk!!!