I think it may be the tip, but also could be a number of things. I say this cause out here all the purple HF guns come with only a 1.5 tip. I don't think they make a 1.3-1.4. It could be just out here though, not sure. Do you know what size tip it is?
I also think cyclopsblown34 has some good tidbits. With an underpowered compressor the first couple passes will be ok but will quickly bog down, noticeable in atomization and sound of the hiss.