I am having my pulley change this week and have provisionally opted for a 11% reduction. I have however been told that I could opt for something smaller say 15% or 17%. However, I am concern that if I got to these values I will have the supercharger whining constantly even when I would like to cruise the car say at 70mph. Is this the case when you reduce your pulley?

Cruising at 70 in 6th gear the engine will only be doing about 3000 rpms, not enough to make the supercharger whine.

So does a 15% reduction with a GP intercooler sound like a good option to stem my need for more go and not annoying the misses to much with the whine!?!

so does a 15% reduction with a gp intercooler sound like a good option to stem my need for more go and not annoying the misses to much with the whine!?!
Yes :)

I am having my pulley change this week and have provisionally opted for a 11% reduction. I have however been told that I could opt for something smaller say 15% or 17%. However, I am concern that if I got to these values I will have the supercharger whining constantly even when I would like to cruise the car say at 70mph. Is this the case when you reduce your pulley?

I personally would love to hear the constant supercharger whine:p