Upgrade hot-end to achieve higher temps (e.g. for PETG) I'm struggling to get my printer to the temps required for modified PETG (the filament I have is Fillamentum CPE and recommends 255-275 °C), I currently can only reach 245/250 °C even if my target temperature is above that. The hot-end is fully ceramic wrapped and metal (no PTFE liner to worry about) and the printer is in a DIY heat shielded enclosure (non-heated). 

The printer is an old (but gold) Wanhao Duplicator 4 (Rep 1 clone) with a MK8/9 extruder running a custom build of Sailfish. I know there is a firmware cap at 280 °C but that's fine, I don't intend to go above that. 

Bar totally swapping out the extruder assembly what can I do to up the hot-end temperature, upgrade the power supply, heater cartridge?
Most PETG reacts vey badly to temperatures above 255. The typical optimal PETG temperature ranges from 225 to 245. Above that it gets sticky...

If PETG is your goal, you might want to find a filament that is more friendly to your printer. They are pretty cheap, and now you have transitioned to an all-metal hot end, you should be good to go!