It needs the front and rear O2 sensors working right to run best, the rear one will not be outputting right with no cat.
Code will say more than just 'idle air control valve'...........will add what it's doing wrong like over limit, or not able to control idle, or other. You are doing what so many others do and that is interpret code after somebody did thus blowing any true meaning into the water. GET THE EXACT CODE NUMBER, I used to read them for people and commonly had to force them to write the numbers down, people are bound and determined to get in the way of their own self interest. No personal insult intended of course.
NEVER let the person reading your codes interpret them for you! They make incentives based on what they tell you to commonly suggest the higher priced parts. Why reading codes is illegal in California, too many stealing from customers by selling stuff they didn't need based on their interpretation of the codes and why YOU want the exact number, look over his shoulder or bug him to get the exact number, it can be the difference in hundreds of dollars.