Made a big boo-boo due to inexperience.

Bought a head the seller thought was a B18B high compression head. It was ported and polished and rebuilt. The top of the head was flat with no signs of FI ports being filled. I was quite excited because it looked like a great upgrade...

My car before upgrades was this:

B18D with 0.040" pistons (compression of 155 psi for all 4 cylinders)
Standard head with no modifications and standard head gasket
K cam
original exhaust and manifold

Recent Build:

Comparing the old head we realized the new head had a much bigger combustion chamber and a larger exhaust valve. We were too into the build and likely should have stopped but installed it anyways. Turns out it's a 74 F head unique to the Canadian and Euro market, with the 92mm exhaust chambers and 44mm exhaust valves. The FI ports were non-existent. Probably shouldn't have installed it but did anyways.

What I have now:

Same B18D block with 0.040" pistons (120 psi across all 4 (low compression head)
B20F head with 92mm combustion chamber and 44mm valves
K cam
0.030mm head gasket
123GT siamese manifold
2" exhaust

Thoughts:

The car runs pretty well surprisingly. I find it spins much easier and I can rev it a lot better--probably the exhaust improvements. Just not a lot of torque. I'm not upset but more frustrated that I didn't understand the differences in the two heads. I realize the diameter of the pistons and the combustion chambers don't match but I'm likely not going to bore out my block to 2.0 right now.

Should I take my old head and shave it to B18B spec? Upgrade it?

or

Take the B20F off, shave it to B20E specs. Live with the overlap.