This is exactly what I meant by nobody wants to go round & round with you. You are asking the same thing again when the answer is already right in front of you. What's worse is you ask specifically for advice from "racers" then immediately tell us you don't want that kind of advice because you are just doing the occasional trackday. Again, why nobody wants to really spend the time to help you, but I will give it one more go...
I already explained to you about the Ohlins fork oil...
If your friends stock Gen4 was perfect handling and your Gen4 handles like shit then what is different? The work that was done by your suspension tuner?
If you really want us to hold your hand through this then you will need to give us more info.
What are your current sag numbers?
How much preload did you dial in to get that rider sag?
How much do you weigh with or without gear?
What do you have the rebound and compression adjusters set to?
Have you adjusted the ride height of the front forks or shimmed the rear shock?
How much fork tube is showing above the top triple clamp?
How about your friends bike? How does his set-up differ from yours?
What oil level did your tuner put in your forks?
What oil did he use?
Without that info it would be total guesswork on anybody's part to try to help you properly and even with all those questions satisfactorily answered it will still be a difficult task without putting hands on the bike.
Here is the info you need on the proper way to work with a linkage although I am sure you won't take advantage of this level of information and instead will want to use some halfass idea of mixing and matching OEM parts from different bikes to basically find the cheapest possible improvement which also yields the smallest incremental benefit. Somebody else will have to give you that info, but if you want to know the correct and proven way to use a linkage here it is.
Gen 4 ZX-10R 5% Linear Race Link