I haven't seen a confirmed 15.8 run except from the car rags and the very few confirmed 1/4 mile runs on this forum have been in the mid 16s.
Getting a solid 170whp should get you close to the 15.0 mark and I wonder if it can be done with a DCT.
'12 Focus Red Candy SE Sport 5 spd
'99 Toyota 4Runner Sport
'11 Subaru WRX STI Hatch