[serialk11r]

Seems like this project is getting expensive :P

Sorry I forgot what radiator you're using, is it the stock Insight unit? Bigger radiator is definitely preferable to fans coming on or less grill block for sure.

If you're heat soaking and knocking already, that's not great, I would give DIY EGR a shot. EGR has higher gamma and low oxygen which both help reduce knock compared to hot air. The stock cam timing should be near best compromise for EGR, combustion stability and pumping losses, external would EGR allows modified cam timing while retaining (or even increasing) EGR fraction.

You would need some way of not messing up the fuel trims since the Honda ECU doesn't use MAF. There has to be some kind of internal compensation built in, but without knowing how it works, it's hard to say if you can go mess with it and expect it to work. If it has a full fueling compensation table that can be learned for all closed-loop conditions, you don't need precise electronic EGR control.

A crude system to control EGR would be two valves in series: One that varies aperture in proportion to the throttle (to prevent misfires from too much EGR at high vacuum), and one that closes off near full throttle. This will produce decreasing EGR fraction with increasing throttle.

One passive method would be to attempt to meter a relatively constant fraction of EGR except at idle, which can be done with a "carburetor" like mechanism feeding exhaust ahead of the throttle plate. A signal from the idle control valve can shut off the EGR supply, and full throttle can also shut it off.

As far as fuel economy goes, retarding the intake cam by ~30 degrees will drop VE by something like 13%, and if you can get slightly higher EGR dilution, you might be able to get 20% drop in VE. Bringing MAP from 0.5atm to 0.6atm is probably worth something like 3-4% in fuel savings.