02 Isuzu rodeo LS EGR code and p0404,p0405

Good evening. I just bought this auto and the engine light come on. The guy I bought the car said to tighten the gas but the light did not go off. ( i am in the process of buying a new gas cap just in case) I drove the car for a week and while I was driving the car felt like I was pulling a train. I went to check the codes again and it said egr. So I clean the intake that goes to the block and nothing happen so I replaced the EGR. the car is running better but the engine light is still on. Do I need to reset the computer or should the light go off by itself. I don’t know how to reset the computer. Thanks in advance for your help.