I've never seen any car show a Dyno gain with Phenolic spacers, be it for N/A or FI engines.

And it is very hard to feel anything short of a 15 RWHP gain, so I promise you this is not going to do it for you.

It's basically a time proven mod that has worked for every engine in existance starting with spacers for carbs and way before that.

This is not going to appeal to the DD type of user which 90% of owners are. It's to keep temps constant and low. Thus more repeatable performance.