Mahirap mag-block swap... you've got to find someone good at it, and if it's not well done, you could be looking at a high maintenance set-up.

If your original motor hasn't been compromised yet, and you're using it on the road, forget the block-swap, just save up for the B18.

You could, of course, go full exhaust and intake. With the right exhaust, you won't lose any torque. Tapos lightweight pulleys at flywheel, then cams... just don't get cams that are too aggressive, otherwise, say goodbye smooth idle, and hello big gas bills...

You just have to accept (for the meantime) that lunging torque just isn't the SiR's calling... same as I have to accept that I can't hit 160 hp with my stock muffler (aggghhh... the dyno!)