What's the bore & stroke between the engines?
From your list there are lots of areas for lost power & response from these:
-smaller diameter throttle body
-smaller or non straight intake manifold runners
-smaller diameter airbox
-lower flow CFM air filter
-non dished pistons
-crankshaft with a lower stroke
-smaller exhaust manifold/turbo
-non polished or ported cylinder head
Seems like they are limiting power via less air & a controlled less powerful combustion. Plus the turbo recovery and cooling are more crippled.
Last edited by av98; 01-17-2013 at 06:36 PM.