Engine Issues
 

Car has had issues with rough running and power loss when trying to accelerate rapidly for some time.
Air oil separator changed, all plugs and coil packs, oxygen sensors. Fault code showed vario valve timing solenoid on cylinders 1-3. Have also had that changed. Car ran for miles with no issues and then the same problem came back.
My mechanic is at a complete loss now and I'm well out of pocket with no resolution to the problem as yet.
Has anyone else come across this type of thing?

Suggest you give us the full model details of your car(you give none) ,all the current fault codes(seems like many?) and relevant Durametric info. Without that it is just keyboard speculation.
Meanwhile clean or replace the MAF . All the parts you mention are model specific and generic parts may be inappropriate/incorrect so check the part numbers against the correct Porsche # for your model/VIN.You do not need to use the Porsche part but you do need to get the correct Interchange item.O2 sensors and Maf are common mistakes.