boosted cars need 93 and use gas. ive never really had a valve cover gasket leak, just get a new gasket and seal it down good. but in all my cars its been normal to see oil coming up from the cover somewhere, even with new caps they still leak too. Bleed your clutch, fix your leaks, get your car running right. Like said above, its running rich and your using the wrong gas. If you have someone with a reputable shop, they will have a leak detector kit. Its a dye and a uv light you put in the car to detect where the leaks are originating from. Or wash everything down good and start from scratch.