i have a Gasoline odor or smell inside my car when the heater is On..

What is your question?

After getting a used heater core and heater box put in my car i now have a strong gasoline smell in my car when the heater is on??? By my Subaru dealership here in Reno,Nevada... Ok the reason i needed a new heater core and box was the heater was only blowing lukewarm air...

What makes this problem better or worse?

It is worse when engine is Cold...

How long has your 2005 Subaru Outback had this problem?

Just since the replacement of the heater core ...