One CPU core much hotter than the others.

I've read this topic in a few places but just looking for a few opinions. I have a i7-4790k and one core (#1) runs 7-9c hotter than the coolest core. in p95/hwinfo it reads 67.4/76.9/71.7/66.4 as the average over 5 minutes of small fft. I did delid my chip and temperatures still vary the same way, so it's not the TIM. All I can think of is poor manufacturing or a sensor that is off. Temperatures didn't vary on my fx-8350 or i5-4690k nearly as much.

Should I be concerned?
 
thanks. kinda figured. stinks because the hot one is holding me back. 1.235v puts my hot core to 80 degress at load. still testing but it looks like 4.7ghz is stable. fingers crossed @16 min on p95. first time testing at this ghz/v. only using a 212 evo though!