[CBFryman]

50% is unlikely.

and your typical Manual Transmission Total Drivetrain loss is 10-18% FWDand RWD and automatic 15-25% maybe a tad higher if its an ineficent tranny, all AWD's have other than FWD's is a differential to transfer pwoer to the rear and then one to split it to the two rear wheels. i havent seen figures on this but stock STi's arent dynoing 150whp... typical is 220-230whp. which is around a 27% loss for a manual.
Evo VIII's typically dyno around the same and are rated (probably underrated) to 286bhp which yeilds a 23% drive train loss for a manual transmission.
i could continue on to the SRT-4, Audi's, orther subaru's but i wont...
a tiburon which a transversly mounted v6 engine has 171bhp and typically dynos consistnatly around 145whp... so around a 15% power loss for a manual.