Yup I changed to the Delkevic headers and have kept the stock muffler. I am finding it a little loud though. I am sill waiting (from China) for an insert type db killer just to take the edge off the growl a bit. I chose the honeycomb type, not the capped end with holes in type.
I have the Woolich flash on the ECU, removed O2 sensor, fitted K&N air filter, and blanked off the PAIR valves and removed their gubbins'. Also I turned down the fast cold idle a little as it was racing on start up.
Of course one doesn't have to do anything if they change the headers, as Akro and Delk state.
My thoughts on this?
The engine is already running lean on the idle to 5k rev range. Which is causing it to run a little hot, in my opinion. Adding a header and removing the CAT and bread bin has just made it run even leaner but in a shorter rev range, say idle to 4k, in my opinion.
If you had a switch on your bike which put into place the mods mentioned here, so you could ride stock for say 10 miles and then switch the mods on, you would understand immediately why we do it. It feels much smoother and no jerky throttle when trying to slow manoeuvre. It picks up better with a more progressive acceleration and, of course runs and smells cooler.
And while you asked, i changed the god damn awful Dunlops over to Bridgestone S22.
Each to their own i guess, whatever you do, just enjoy!