You can try looking for compatible parts with the Corolla XRS, which has the same engine. I believe there is/was a supercharger available for a little less (~$3k). But I would first make sure the engine is in good condition.
Stumbling or slow off-the-line performance is usually due to gummed up EGR, IAC, or other related parts. If you have any type Bosch Pt plugs, trash them and get the OEM ones...seriously they're junk. Go for a good tune-up, checking all the wires are in good condition, no vacuum hose leaks, etc. Check that the coils are all working too.
If the car has high miles, and alot of it hard driving, then maybe time for a transmission rebuild. You don't mention an auto or manual...sometimes a fresh fluid change can help. DO NOT OPT FOR A POWER FLUSH. Just drain, refill, run for 25-50 miles, and drain/refill again. Or use the stickies at the top for directions to flush it yourself with a reservoir of fluid and a catch pan.
Hope this helps!