[Isphius]

Yes, You wont need 18psi for drifting. And yes just get him to rebuild it to stock trim. Or just get an upgraded compressor if anything. The mk3 wouldnt be my first pick for drifting, These cars were designed to stay in comtrol, It can be done as in any car, But they dont really have the slideability or steering lock that the smaller cars do, Like the ae86 corolla or 240 sx. But to answer your other question, It wont hurt the turbo to restrict the boost, Its actually easier on the turbo. Just get an electronic boost controller and set it as low as you want.