RWD turbo yeah. First thing, you can't get power without it effecting your insurance. You can get power and not tell your insurance but thats up to you.

The basics would be a stage one setup which would free up your engine and allow it rev better freeing up a little power.

Stage two would take you to 270hp with increased boost and better all round drive-ability.

Stage three is around 330hp and is about the safest you can take a standard cossie lump too without running into problems. It is generally recommended to upgrade the headgasket at this point (group A/WRC/cometic) and some people advice fitting group A studs and nuts whereas others say the standard stretch bolts are safe to use. Its up too you though.

You can also modifi internals and carry out some head work but things start to get expensive.

Phone around a couple of companies to find exact prices as they do vary. Some popular companies are Castle Performanc, PJ motorsport, Motorsport developements (run by Stu who also part runs this baord) and MA developements.

But as said, any increase in power will affect your insurance.