Some seem to forget that the Germans didn't have the needed chemicals to obtain the required octane level for their plane engines.
They made "ersatz" chemicals which pushed the octane level above 100 whilst the normal level being 87 Roz.
This means that any captured plane did perform less than flying on high octane German fuel especially all Fokker D VII.
Some Dr.I were equipped with the Goebel Goe engine 145 ps which nullified the drag as the cylinders turned in the opposite direction of the propeller.
Some aces like Jacobs installed a captured Clerget engine which boosted the plane's performance quite a lot.