will u take 350 for just the turbo??

You can but your also gone to need a head gasket and while your doing that you might as well replace your head studs with arp. Now for the oil leaking it could just be your valve cover gasket leaking threw or maybe a small crack in the valve cover I would remove it and check it out. Now it may be sluggish due to a boost leak I would test it and spray with soapy water and looks for some or it, would be due to a exhaust leak. If I were you I would fix every leak first then try it. Do you have the boost gauge installed and a manual boost controller.?