p0133=o2 sensor bank 1 sensor 1 slow response

p0401= egr flow insufficient

i am getting both these codes and i am wondering if anyone ever had both these codes thrown at the same time? Any suggestions what i should do first? Could the o2 sensor cause the egr problem or vis versa? Any help would be great. Also what kind of egr do we have in the celica do we have a ported egr valve, negative back pressure or positive back pressure?