You can bore it out for 2.0 pistons & fit the 2.0 crankshaft (you have to cut the bottom of the cylinders to clear the rods + trim the timing wheel to fit). It really isn't worth it though imo.
1.8/2.0 cams plus a Supersprint manifold gives about 150 Bhp, looking back that was about the best balance for reliability, the power level was just right for the chassis.