What is a more important criteria to follow when picking out the closest map to your exhaust set up?

For example if I have a 2 into 1 with no close match, but find a 2 into 2 exhaust with the same exact headers I'm running, will that map run good even though it's a 2 into 2? Or am I still better off using a 2 into 1 map even though though is no close match?

I've heard people tell me that the headers were the most important, but others tell me the the over length vs 2-1/2-2....

 

Most important matches are the engine size, cams and injectors. Air cleaner makes no difference (assuming its non-stock and flows good enough). Exhaust is something that ideally needs tuning on a dyno. I'd pick a close map and then either 1) call it good or 2) if your tuner has it, use auto-tune to bring it close or 3) dyno it.

 

I'm going to get it dyno'd in the spring but for now am I better off using the 2 into 2 map with the same headers as my exhaust or a 2-1 map where the exhaust match isn't close?