Here is the video of the GS4 v.5 retrofitted with cylinder upgrades.
Shop work prior in preparation for the run (next will be cross porting):
Original set vs. re-ported
Air testing the cylinder setup
This clip was timed at 30 sec per lap that equates to 158 smph. This setup is very impressive, I have never seen an engine with the also immediate throttle response, torque and ability to reach full speed in such a timely manner.
Reflecting back several years ago, when we reviewed this engine for SitG. Here you can see the original performance level vs. the GS4v.5 in the prior video.