It had more weight and a different power rating on the engine.
The FW-190A5 had the same power as a post June 1942 FW-190A3. You will find some sources that claim the lengthening was done to improve cooling. That is most likely NOT the case. The problem the BMW801 was experiencing in the FW-190 installation at this time was too much cooling. The front bank of cylinders ran much cooler than they were supposed too creating a temperature imbalance. This was later corrected by the addition of an attenuating ring along with different fuel formulas for summer / winter.
The only changes to the motor between the FW-190A3 and the FW-190A5 are fuel changes improving knock limited performance, change to the Kommandogerät operation of the supercharger gearing, and changes to the mixture regulations for the new fuels.
Now C3 Einspritzung appears on the FW190G and F series along with the zustatzkraftstoffbehälter im rumpf. The tank causes instability when full and is not required for C3 Einspritzung installation. Some FW-190G's reach speeds of 585kph at sea level with empty racks.
That is running like a raped ape at tree top level for a 1943 ground attack platform.
All the best,
Crumpp