I didn't read your original post closely enough, so I'll modify my advice.

If you do NOT see air bubbles between the tank and remote needle valve, then replacing the tank lines probably won't do anything. So check the bubble location(s) first. If they are only after the needle, then the above advice is likely correct. The "O" Ring on the needle is bad. As FH mentioned, placing a piece of fuel tubing over the needle could well correct it.

The line between the needle and carb could still have a pinhole in it, so if the tubing over the needle doesn't work, replace that.

As Kirk mentioned, be sure to hold the nose of the plane up at full throttle to be sure you're not set too lean. I've found that I have to run my engines quite a bit richer in cold weather.

One Other Thought!
Depending on HOW cold it is, the cold air could also be cooling the engine too much in flight, which will put out the glow plug. So you might also try wrapping a little aluminum foil around the cooling fins on the head.

Good luck,
Dennis-