Check this thread: Post 13
https://www.northamericanmotoring.co...ed-at-80k.html

 

Thanks, I have 125,00 on the clock and no issues but I am going to look into doing this soon!

 

Hi Steffen,
I stumbled upon your post after searching long and hard. I too have exactly the same problem with my cooper s, it is a 2005 model with auto transmission. Since having the 17% pulley kit fitted I am getting the same symptoms as you, almost like a momentary pause/cut in power at about 4000rpm till just after, then bang pulls hard again. I drive in manual sport mode all the time so I know this is not kick down. I've recently had a remap to see if that would sort it but no luck and I've just fitted a new bypass valve but still no luck. The car has only covered 41,000 miles so I cannot see this being a transmission problem. I am running out of ideas. The autos are much less common in the UK so I am having trouble reaching out to anyone over here with any kind of answers. Did you manage to get to the bottom of it? I would really appreciate and kind of help.
cheers
Zach

 

Try gapping your plugs @ .55, then try it at .60, then last @ .65. When you do this run your car for a day or so just to get the feel of each. With the MSD pack, .60 is where you might have your best luck. But every car is different.