I have a 2005 Magnum RT, It has some minor mods, TB spacer, shortie coil wires, Shortie headers.Borla exhaust, Fresh air kit, 165deg Therm and a Diablo Tuner set to max performance. It runs great no complaints on running
Im having a progressive problem that when the ambient temp is 0-20deg F it simply wont start, 20-30 just hard to start. It cranks over fine but pops and farts in the pipes. Once it does start, you can tell it was flooded. I have found if I take a hair drier and place it under the engine cover for 5-10 min it starts up. and once it starts it runs fine. So I have replace the plugs, Used inj cleaner, Installed a new battery, cleaned the TB. and given a good once over for potential causes. any body have a similar experience?

Codes? Monitor coolant temperature with a scanner and verify correct fuel pressure.

I can't remember if there's an ambient air sensor on those. If there are, you may want to look into this

I would look at intake air temp and coolant temp on a scanner to verify they are reporting the cold correctly.

If that all looks fine you might try loading the stock tune back into it, if that fixes it call diablo.