SR20 But you'll need a transmission from the US or Japan that fits.

QG13 if you can find it. But you'll also need the computer box that goes with the engine. Best really, is just to get another QG16, or fix what's wrong with yours.

Get a second opinion, do a compression test, then a leakdown test to determine where your problem is. Likely the piston rings weren't set right or are the wrong size.