Hello There:
Welcome to Porsche 911SC ownership!!
First and foremost, did the car come with records ?
If it did, then my best advice is to read all the records to assess where/when the last complete service was done on the car.
Specifically, the engine compartment, when was the spark plugs changed (USE COPPER) when was the Air Filter, Oil Filter, Oil drained and replaced with new ?
Plug wires could be old and may cause issues. Fuel filter may be old and need changing, especially since you mentioned the "lag" when accelerating.
If none of the above have been done recently, start simple with new copper plugs Bosch 999-170-165-90-M14 Spark Plugs WR-5-DC+ <
You will need a timing light in order to complete the task.
Basically, set the valves per specifications, add the new copper plugs (if not new relatively new already), install new valve cover gaskets. Then, set the timing using the timing light...this requires adjusting the fuel intake in the process; 950 +-50 RPM.
I believe you may find there is nothing wrong. However, if you still have issues after what is said here AND by what is SAID ABOVE...post results again.
Most importantly, as mentioned read all of the documentation that came with the car so you know where you stand with your next service. Also, buy the Bentley for the 911SC it has been a wealth of knowledge for me to learn about this model.
Hope this helps and Good luck.
