Minor improvement--
Piggy back ecu, muffler, intake

More, in order of cost. Having investigated this myself a few years ago I think the above cost figures are optimistic --
Bore out, 2.2L should be ok, up to 2.5L maybe.
Blueprint- balance pistons and crank, valve springs to get it to rev higher
Change motor to 2.5 L (3litre is better if you can get)
Turbo kit
Supercharger kit
Change motor to turbo (half cut)

Compared to trade up, what is cost effective? None of the above even doing all work yourself.
But if you have fallen in love with the car and that is you thing, do it and good luck and we’d be keen to get the story.