The system for vehicle grade also changed for S15, now using simply SpecS and SpecR A feature that is rarely seen on OEM vehicle's but could be had on the S15 Silvia is a gauge in the Apillar garnish The SpecS was for the normally aspirated engine and the SpecR for the turbocharged engineAnd a second tuned version was based on the SpecS trim level with the engine output increased to 0 hp (150 kW) through the use of increased compression, more well if i was to convert my s15 spec s to a spec r would i have to strengthen the chasis or is it strong enough as it is ??? Jdm Gold Rare Silvia S15 Autech Parts Srde Rwd 6 Speed With 0hp Drag International S15 spec r autech