The only thing which usually causes that sort of behavior without throwing any sort of code is the MAF. The ECM is totally dependent on it, so even a piece of lint or a butterfly wing can result in a car that barely runs or doesn't run at all. The cam and crank sensors can also act up without throwing codes, but the behavior is usually different, unexpected stalling and hot or cold no-starts.
Yah, it could. A stuck-open Purge Valve will act like a hidden vacuum leak, except it's sucking air from the fuel tank and evap instead of the outside world. That won't matter as much in open-loop operation when the engine is cold because the ECM is providing artificial enrichment. Once it tries to go closed-loop the enrichment stops and it will act like a leak at low RPM's.