Same basic motor, Just some design differences to fit in the IS's engine bay. Don't quote me on this but I think the gs 3.0 l6 is rated @220 hp and the is is rated @215 hp.
Yea edmunds said the 03 IS is rated at 218. Should i be happy or sad. I went from 85,000 to 18,000
Well, You did gain 67k, What warranty did they provide ? I don't think one could tell by the seat of his/her pants. I wouldn't be too concerned about how the engine was treated prior to the install, Most likely cared for at a dealer. Did you get the history of the transplant ?