My car is backfiring and hesitating. I need help because I just put a high flow converter on it last year but I think it might be the problem. Is there anything else that could cause it to do this?

 

Your car can't backfire. It's fuel injected.
No, there are a number of things that can cause misfires. Start with a tune-up. See if that helps.

 

I changed the plugs, plug wires, cleaned the filter and changed the oil. Its still miss-firing. I also changed the distributor not long ago so its all new. Would cleaning the IACV help clear this up possibly?

 

Check the ignition timing.

 

What type of distributor did you buy, OEM replacement or reman? I have seen a few of the cheaper reman distributors fail out of the box. Electrical components are easy enough to test.

Just a few things you could check;
• Ignition components (doesn't matter if they are new, it's cheap and easy to test them)
• Timing
• Fuel system (pressure, filter & injectors)
• Valve clearances
• Vacuum leak
• Exhaust leak (before primary O2 sensor)

 

check for engine misfire codes. Do what most have already mentioned. Double check your work. make sure your plug wires are in the correct location. check your timing n vacuum leaks.