Motor swap happening, need to make a few changes
 

I have a K20 swapped Insight 11.5:1cr, 6psi boost, Accord 1-5 gearing with 4.1 FD, fun car but the clutch is a tad too stiff for the daily grind so Im switching to K24a4 in stock form tuned on Kpro for 87.

I will be changing the 4.1 to a 3.4 FD and switching to a factory style clutch. I've read up a bit on flywheel weight but wanted to run it past the peanut gallery as well.

Car weighs 1850 with Kswap, //////

Flywheels thay come on K24a4 are Accord @20lbs and Element @24lbs, non a4s are TSX @22lbs and RSX @16lbs..... what is best?

I will also be ditching the turbo and have several header choices, first fact is K24a4 is 160hp, the RSX/EP3 style headers are what fits, K20a3 is 160HP, K20a2 is 200hp, header is identical with exception of slightly fatter tubes.... Or I can use one of the many full length that would fit an RSX....

This car is (for lack of a better description) too fast and even if I choose all the least HP pathways it will still be fast, that said I want the best MPG I can get otherwise. I plan on exhaust being as quiet as possible but again will make some sacrifices for better mileage.... Thanks for any advice, opinions, questions regarding etc

Regarding flywheel weight, you'll notice from your own data that heavier flywheels are generally mated to heavier vehicles. Given that your car is quite light, I would opt for the lightest stock flywheel you can get your hands on to provide a more sporty feel.

For headers, consider the HP and engine speed you want to maximize. If you prefer mpg, generally smaller and longer tubes will provide more exhaust velocity and thus low/mid torque. High revs will benefit from short header length.

I have no opinion on headers (I'm using the stock one that came with my K24) except to comment that the OEM cast iron pieces are indestructible, but also heavy. Many aftermarket stainless are known to crack at the welds where the pipe meets the flange.

Given that I can weld (albeit poorly), I would consider a stainless piece to save weight, personally.

As for flywheels, I had the same logic - it's a big engine in a light car, shouldn't need practically any flywheel at all, right? Thing is, while an RSX weighs 50% more, your 3.4 final drive makes your 1st gear 40% taller, so the drivability is just about the same. I also downsized my crank damper/pulley, removed the balance shafts, and there's no power steering pump, so the rotating assembly doesn't have a lot of mass. My 10.25lb flywheel is fine, but it's definitely easier to stall than the 3 cylinder was. I'd say don't go any lighter than what I have. 10lbs is fine for something more sporty, but I think 16lbs is more appropriate for an easy-going daily driver.