The car in question is a '92 GSR with a B17A. So no, putting a B20Z in will not increase the power. I would go to a shop and see what they think is wrong with it. If something inside the block is shot, a B18C1 shortblock (just the block, nothing else) will bolt in place of the B17A shortblock and provide a bit more power. If the B17A crank is still in alright shape you can sometimes sell them on thepartstrader.com or eBay for a decent sum because of their rarity.