your looking to get an extra 60bhp from the engine, that is a lot of hp no matter what the funds, my honest opinion is buy a new engine, if you got a 2.8 thats 190bhp straight away, new inlet manifold, remap, exaust, induction kit etc will take you to around 230bhp depending on the donor engine and quality of parts used. that would set you back around 1k, engines are 4-500 and then the bolt on parts are around another 500, its a relativly straight swap and you would only need to source a few parts to complete it, otherwise your looking at in excess of 2k to carry out the work to the 1.8, not to mention the life span issues of the engine once tuned. another thing to bear in mind, getting past 200bhp from the 1.8 will be expensive, getting past 230 to the 2.8 isnt as bad.
bit of a recap, 1k to get 230bhp with a new engine, 2k+ to get 200