This works w/all the non-EGR EJ22's (most manual cars from '95-98, and any '90-94 EJ22) and should work on the non-EGR JDM EJ25's, too,  and doesn't require drilling/tapping the driver's-side cylinder head. (You'll need to get a single-port exhaust header/y-pipe for the '96-'98 EJ22.) BUT REQUIRES an EGR-equipped intake manifold ('95-98) from another EJ22.   EGR = Exhaust Gas Recirculation valve   Edit: Also, the EJ18 from the Impreza should work. (Thanks to Matt167 for the reminder.) But be