IF your car is not a turbo, a good mod for the N/A's is the turbo exhaust. It's 2.25" and a bit larger in diameter than the N/A exhaust, with a deeper tone due to it's larger diameter.

Next, try a K&N drop in panel (air) filter. Not much performance gain there, but it's good to have an air filter that you can just clean and re-use.

Next off, IF the car is not a turbo, get Bosch Platinum +4 spark plugs, 8.5mm to 9mm plug wires etc.

If your engine is in good tune, injectors are clean, fuel pressure is good, cat is not clogged, then you should be up around the 120 - 125 hp range. Still 30 - 40 hp short of the turbo's, but more than the 114 that it came with.

Without getting a more wild cam, there's not much more you can do short of adding N2O. You can get an adjustable camshaft timing gear for your stock camshaft, but in all honesty, you don't need it unless you have a "more wild than stock" camshaft. Lets just say you need a valve adjustment, and figure "what the heck, why not throw a cam in there" then you could see, with a camshaft alone and the other mods I mentioned, up to 140 hp at higher RPM's. The camshaft to get would be the Volvo factory sport cam called the VX. IF you DO NOT have the distributor on the head towards the firewall (i.e. your distributor is on the drivers side of the block), then there's multitudes more camshafts you could use, namely the A cam, B cam or even K cam if you like lumpy idles and maxing out horsepower around 6000 rpm like a big block Honda.

IF your car is a turbo, then it's a whole different beast and although the afforementioned mods will work (save the exhaust) there are other mods that can be done to spice it up, mainly having to do with boost.

Good luck with it

Ryan