I reinstalled the GPZ springs after stretching them out a bit so they increased in set about 5mm longer in overall free length. I like the overall performance of the stretched GPZ springs better than the OEM springs, so they are staying in for now.
There is still a mild lean spike with the stretched GPZ springs, which I can see on the A/F meter, but there is no hesitation & but for the meter I wouldn't know it was there.
I plan to test some other springs within the next week or two. Stay tuned!
