The fourth-generation engine uses a proprietary CT15B turbocharger. This generation was used in the Toyota Caldina GT-T AWD Wagon (ST215). The exhaust housing is actually cast into the cylinder exhaust manifold, rather than the normal practice of a separate turbine housing after the cylinder exhaust manifold. Due to this, the CT15 is backwards compatible with the third-generation 3S-GTE cylinder head only, not either the first or second generation. Intake charge was cooled by an air-to-air top-mounted intercooler fed through a new side-feed intake manifold. This generation utilizes a coil-on-plug ignition system and 550 cc injectors. Boost remains at 13-14 psi, however overboost fuel cut is increased to 21 psi. Compression is increased to 9:1 and produces and .