Ultraspeed, you can purchase just the button head and make your standard engine a turbo.

Pooldoc, first switch to hotter plugs, that will really help the idling, O.S. p3 or O'donnel 77t. Then try addidng a shim and see if that helps with the plugs, While you have it apart be sure and check your idle gap and make sure its within 1mm-1.5mm. so you can make sure your tune is correct.

Satoch, it may be a good idea to check the rear bearing and see if it is in good shape. Pulling the thin head shim should help.