1999 Toyota Corolla Engine check light (ECL) on since Jan 1

Engine Mechanical problem
1999 Toyota Corolla 4 cyl Front Wheel Drive Automatic

I have been driving 99 corolla since 2001. Right now it has 117,000 miles. I never had any problem with this car untill Jan 19th, 2009. I hit a pothole and my engine check light (ECL) came on after a minute or so. I took the car to the toyota dealer next day morning and was told to replace the Catalytic converter (P0442). I did so in next few days. After a few weeks ECL came back. I took it to the dealer and I was told that it was a EVAP problem (P0441) and I may not have properly fitted the gas cap. Same day in the afternoon the ECL was on again 3rd time. Again I went to the dealer and this time I was told the probelm was with the purge valve (P0446) and it needs to be replaced. The dealer cleaned the purge valve and I was told that I have to replace the purge valve if Engine light comes back on again. Well after a week as usual engine light came back on. The dealer is advising to replace the purge valve. For a second opinion I went to the local autorepair shop. After running the daignostic test I was told that I may need to replace the sensor and the hoses (Codes P0441 and P0446). I was told that purge valve is fine. Both the dealer and the manager of the local autorepair told that car is going run fine even without fixing this problem. I run a search of the diagnostic codes and found that 99 corolla have a probelm in the electronic control module (ECM). Toyotta issued a service technical bulletin in 99 to have it replaced and this service was covered till 96 weeks or 80,000 miles. Now I am sure the problem is due to ECM and not anything else. Plus I can, t take advantage of toyota TSB. I shall be grateful if you can provide me a feedback so that I can rectify this problem.