BP says today they have traced the source of the bad gas back to the alkylation unit at it's Whiting refinery.  BP says it has made operational changes at the pant to fix the problem and now fuel produced there is back within normal specifications.  The company says it continues to systematically inspect and test the distribution system served by the refinery, as well as test the gasoline to ensure quality.  BP also says it has begun paying claims and is following up with consumers who have contacted the company.  The company says any consumer who purchased off-specification fuel wishing to file a claim should call 1-800-333-3991 or 1-800-599-9040 to speak to a claims representative.  BP reminds consumers they should save sales receipts, credit/debit card records and repair bills.   Consumers can also access info and submit an online inquiry at www.bpresponse.com.