Lets say in 1942 in Russia the 4th Panzer army wasn't diverted to cross the Don, the Germans take Stalingrad earlier and have more reserves to watch the flanks. Stalingrad isn't encircled, the Germans might get pushed back in the Winter due to covering multiple threats but no big encirclement and no big airlift.
Could all those transport aircraft and extra reserves thus available make the German effort in Tunisia much better in December - February 1943 when they still could compete????
Assume:
Since 320 JU52s were used in the Stalingrad airlift during that period, lets assume here half of that total (160) are available starting in December 1942. Due to rail limitations most of the transports have to fly from the Naples area to Tunisia. Allied airpower would be able to shoot down most of them from April 1943 on but until then the attrition rate is acceptable.