My dyno guy reckons 15% loss on a T5 and 8.8 rear end with
synthetic lube. If yours is a top loader or older design trans and with the Jag rear I would bet that your drive train loss is a fair bit higher. If I had to guess I would say around 25%. If it's as high as 40% then you have a real problem. 40% sounds like an auto trans number. It will be much higher with an auto trans compared to a stick.