There are lots of good reports about the results with Godspeeds. You will find some searching here. I believe the Godspeeds were originally designed by a Aussie 300ZX owner looking for a bigger, affordable IC. The quality control was actually pretty good. This was many years ago. Not sure what the quality is now. Not sure if still the original manufacturer.
Seb at SZ tuned bothy Zs on Godspeeds and told me he was impressed with their performance