I have a similar problem with my S1 Sovereign. Starts ok , runs ok, but smokes when revved, Did a comp test and all low (sub 100) but no difference when oil squirted down bores. Suggests valves. But did leak down test and no issues anywhere, valves , rings, gasket. Mechanic who did test thinks it likely stuck rings as engine not previously run for some 5-6 years prior to my purchase, although he can’t explain why squirting oil didn’t improve the readings. His recommendation was to pour some " mechanic in a can" type product in the cylinders and drive the car gently to see if there’s any improvement. Maybe the same issue with yours, rings just stuck.