If you can't afford a 180 then tbh the only turbo ZS within reach would be a turbo deisel. Even if you did go ahead and slap a turbo on the K4 1.6 it would cost you more than buying a 180. Not to mention the insurance premiums. You could drop in a 1.8 turbo from a ZT but they only make 160bhp so unless you spend loads of money on that, it will be out performed by a 180 anyway. If you're handy with a spanner and have space in the garage, get a T series and rebuild it yourself. Pay a company (AA Autosport etc) to drop it in your engine bay and they will sort out the electrics. You will have an engine capable of well over 300bhp if you build it with power in mind. No K4 or KV6 can match the T series for tuning potential.