Primarily the stamped/welded exhaust manifold (versus a real header on the GS300) and single-muffler exhaust.Originally posted by Risk3233:
What did Lexus do to the IS 300 motor so that it puts out less HP (I belive 10 HP) than the GS 300?
Simple, sure. Bolt-on a real header and a less restrictive exhaust. But since all three catalytic converters are integrated into the stamped/welded exhaust manifold and front exhaust pipe assembly, a street-legal header would need to incorporate and be sold with one or more cats. Read: very expensive.Originally posted by Risk3233:
Would it be simple/cheap to get back the lost 10 HP that the GS has?