The 7K engine is a 1.8L one, which has a longer stroke rather than bore...and this makes it less responsive to being revved, etc, in comparison to other engines. Plus it turns out a maximum of 80 odd bhp and around 100+ lb-ft of torque. In a car that is as big as a Mark II, this is not going to give you much in the way of performance. However, at the very outset, let me also say that economy and performance can rarely go together. If you want performance, you'll have to sacrifice economy...and the same is true for vice versa. As for what suits you best...why not try to do some research on a normally-aspirated 1JZ? It's six cylinders, has decent hp and torque, and is comparatively economical when compared to other higher-performance engines. Best of luck.