Thanks Doctorturbo, you've always got the info I'm looking for. I don't know if I'll try it, just wondered why there doesn't seem much on info on the net about it. Right now I've got my motor apart and I'm looking at what a lousy head design the DS has. Could they have gotten a bigger right angle approach to the valves?

 

I was blown away how much metal was in the exhaust port area that needed to be taken away, I was wondering also why the factory woukd have such a design its like they wanted to choke the motor, lots of flow can happen when they get opened and cleaned up.
Ill just stay with my 110 leaded octane!!