My 86 E16 S pulsar has 11M castings and the tags on the body are japanese. I dont know if the pulsars were all made in japan or what, but the cylandar heads are the swirl type as far as i can tell. Are there heads that are wide open on the intake side? Swirl is good, but it looks a little too restrictive to me. What would be the best cylandar head choice?