5.3, rebuilt fewer than 1500 miles ago.

Recently got a CEL with a P0327 code. It happened a day after putting in ~5 gallons at a gas station with whose fuel I've had problems in the past, but I was in a hurry. I always use regular non-ethanol (flex or not, I dislike corn gas.) Anyway, thankfully I didn't fill up there so I headed straight to the only station within 50 miles that has 91+ Premium and topped off the tank hoping it would take care of the problem.

Today it started and ran much better until it reached operating temperature at which point it lost some acceleration and sounded awful while idling.

Is there anything I can do before I'm forced to change the sensors? I know removing the intake manifold isn't a huge job, but doing a proper job of cleaning the heads and sensor wells is still fairly time-consuming (I hear it's around 3 hours at least) and the heat here lately makes it unfeasible for an amateur working in the driveway.

Thanks for any help.

 

Check your fuel pressure. If yours has a external fuel filter then change it.
Knock sensor will not really affect regular engine performance.

 

Update in case someone with a similar problem comes across this. I tracked it down to a crossthreaded spark plug. Despite lots of PB Blaster and very gently removing it, the cylinder head is going to need a rethread. Thankfully it has enough left to hold a spark plug until this unbearable heatwave passes and I can work on it outside.