Depends on how much extra power you are looking for. I have a B20E which is the highest output version of the B20. It is more powerful than a B20B; but, not by a lot and its still a noisy engine with a narrow power band (compared to modern engines). If you are looking for significant reliable power increases your low cost solution will be a more modern engine transplant. Picking an engine and gear box from a car with a similar in-line engine configuration will make life simpler. A Mazda MX5 or Saturn Vue / Pontiac Solstice come to mind (salvaged MX5s can be hard to find). The turbo versions of the Vue / Solstice would toast the Dana 30 differential so stay away from them unless you want to do a complete drive train. There are other options such as the Ford Lima engine. The Volvo B230FT engine is possible; but, probably more work because of its tilt (turbo interference with the right inner fender) and the intake manifold - brake booster interference.