Spark plug cans

[lutronjim]

I have a 'connect and cruise' package installed in my 70 C10 chev truck - LC9 and 65e tranny. I have headers installed and 3 plugs had to have the can and 'boot' removed because they kit the headers.

I am having loss of power at high altitudes and skipping - above 3000' or so.

Chevy dealer claims its because the cans are missing, spark is jumping to headers. The is at least 1/2 inch between the wire and header. Since the plug gap is maybe .060 inches this doesn't seen possible to me. They claim the load on the engine is causing the spark to jump.

Does anybody know the real purpose of the cans and boots? I have heard radio interference suppression and wire insulators because of heat.

Thanks