I recently got a code p0440 showing evap malfunction,then a p0442 showing evap small leak.Does anyone know where to start and most important will it affect the performance of the car???

Best place to start would be the gas cap. Check the seal and make sure it tightens correctly. Anything past that would need the evap system filled with nitrogen smoke to locate the leak and a scan tool to activate solenoids to check function. Other common things to go bad are the vent solenoid and the purge solenoid. It won't really effect any performance, but if you have emissions testing it will fail.

would a cat converter throw these codes???I recently had to punch the converter out because it got clogged .

Catalytic converter would set a p0420 code, catalyst efficiency, if the system reads the cat is not doing it's job. Plugged cats cause performance issues, but both are unrelated to the emissions system. The evap system consists of the purge solenoid, vent solenoid, the lines, and a charcoal canister.

is there any good place to start on troubleshooting this code???:confused:

Start with the gas cap and make sure it tightens properly and the seal is good. Personally I would just go to the dealership and buy a new gas cap and throw it on. They are cheap enough. Don't buy the cheap made junk gas caps from autozone, o'reilys, etc. They can cause the same problems.