Aftermarket turbo kits:
- The TTE Turbo kit from Toyota. This one has approval from Toyota and doesn't loose your warranty on the car. Its ~184bhp and they also add various additional bits of bracing to the car. Not available in the US (?)
- The Hass Autoworks kit - Based on a GT-25 Turbo. Probably one of the first independent tuner kits - Hass are based in the USA. There's quite a long wait for kits to be delivered, but they are available in the UK. This one produces good power figures from low boost due to the turbos relatively large size - 250bhp is easily possible.
- The Power Enterprises kit. This is based on a small IHI turbo and is designed to be bolted on with minimal effort. The kit has had some customisation and includes a chargecooler and fifth injector. Its running 220bhp @ 7psi - I think the kit as standard out of the box offers 190bhp.
- Monkeywrench Racing offers a GT28-based 1ZZ turbo kit for the MR2 Spyder. Cost is nearly $4,000 but the kit includes everything needed except the fuel management and injectors. Power claims are 245-275hp at the wheels at 8-10 psi and up to 340whp with supporting modifications.