I have the 2.5 SOHC, the torque is pretty flat for either engine. I'm trying to find charts for before and after header on the 2.5 sohc. I know i've seen them before. I believe it was in the range of a consistent 5-8 torque gain and ~10hp at the peak, and a few on the low end.
The intake tubing for my subaru has also been modified, result yielded worth wild difference in pull especially on hills.
Probably being subaru could fart up the hills in 4th @ 1700-2000 rpm, but instead it dumps to third and runs up to 2700-2800rpm, which the car begins to poop fuel economy at and above 3K.