I failed my emissions on a 95 accord lx, the reason was NOx was too high

25/25 NOx Allowed 945 Mines 1323
50/15 NOx Allowed 1045 Mines 1307

I have a magnaflow flow cat and magan headers

any ideas? i took it to a shop the guy said im sure its the cat converter? if that is the problem will it be ok if i get the magnaflow direct-fit 22636 cat instead of the honda oem. thanks