AFTER you change the plugs and you still get a E-27........check your coils,these k21/25 engines will run decent on 3 cylinders and you might not notice it except for lower power output. The way I check them is I start and run the engine,the one at a time I will unplug the connector from a coil a listen for a RPM drop in the engine,you will get a code E-34 doing this biput that can be cleared once finished.....if you find a coil that dosent drop the RPM's when it's unplugged the install a new one