Check engine light
 

I had a p0430 engine code in my 2000 gs300. i replaced the cats and one of the o2 sensorsthinking that was the problem because my friend said i was blowing white smoke when i got on it. after i drove it about a hundred miles the check engine light came back on now i dont know what the problem is. i cant afford to take the car to a shop to get it worked on. please help