2011 altima coupe engine began intermittently running rough - Check engine light came on - it was a po301 code - changed all plugs and coils - light went off cause I disconnected battery while doing this - then CEL came back - engine still intermittently running rough - po301 again - cleaned MAS with can of CRC - no difference - maybe injector getting clogged - had shop clean injector with this device that gets hooked up to fuel line then they run some stuff thru it - CEL was off for 5 days, ran great, then I felt a shudder and the CEL was back on again. The car runs good but it seems to hesitate when I get off the gas - It must be something more serious, could it be a head gasket problem? Any suggestions?

The head gasket is easy to check on a QR25, just pull the plugs and look down the holes with a flashlight. The piston crowns should all be a matte black color, if any of them are shiny or have large, shiny spots then the head gasket is leaking and blowing the carbon off the crown.

Thanks for that - I'll report back when completed.