I just put 2 coats of UPP on 2 weeks ago and used the 4 star spray wax with carnuba on it after washes.I am wanting to add another coat and was wondering if the UPP would seal correctly since i used the spray wax with carnuba in it?
I don't think that it will seal correctly, but it will not hurt anything either. It will look fine, but if you want maximum durability out of that *layer* then you might not get it. Give it a go and let us know how it turns out.
I would wait a week or so after applying the spray wax (are you referring to 4* Ultimate Gloss Enhancer?). Then wash the car before applying any more UPP. After a week and a wash, most or all of the carnauba will probably be gone already. Sealants do not work well over carnauba.
I still agree with my statement above though. Typically, spray waxes don't last very long, so I'd just wait a week or so and then wash the car. Then proceed with more UPP.