spectra premium heater core issue ? / anyone recommend a good heater core ?

I have had pretty good luck Spectra, that being said you have to eliminate other issues before you blame the core. is your cooling system full of sludge and scale that will block the core? take the core and hold it next to a new one, it will feel heavier than the empty one. is the head gaskets pressurizing the system causing the seams to blow? the heater core is designed to withstand a certain PSI of pressure. If your car checks out, then it probably could be a bad core. Try a new one, I am assuming they are inexpensive enough, or take it back and exchange it. Parts are made overseas now and quality can be questionable,