P0300

[sv650steve]

My car has been having a flashing check engine light and misfire as soon as I get on the highway after leaving work. It previously had a P0456. i've been having trouble chasing down the P0456 and it comes on and off, but my car never had any kind of misfire before (tried replacing the gas cap and purge solenoid) condition did not improve. I don't have a clue if these two are related but they did not show up at the same time. The spark plugs are 6 months old. New CPS, and CTS (did not improve misfire). It's also throwing codes for misfire on cylinder 2 and 4. It seems to not get any gas as soon as I rev it but this goes away in around 20 seconds. Gas has been refilled since problem started. Within the last two weeks i de-greased my engine bay and under my gas cap cover. Any ideas?