Is there a VA provision that covers cancer or respiratory issues related to JP4 burn pit training and AFFF exposure?

There are a number of presumptive conditions, but none specifically for your situation.

Presumptive conditions have three components - an certain ongoing illness/injury, a certain time of service and a certain location/condition of service. Some of those components are very broad (i.e., any former POW (time/condition) that suffers from anxiety) or are very narrow.

If you don't fit into one of the 'presumptive' categories, then you will need to show a service nexus - something that shows the condition you are suffering from now was caused (directly or indirectly) by your military service. For example (this is hypothetical), if you have had documented exposure in your records to radiation and now have one of the forms of cancer that might develop from that exposure.

Since you were in the military during the 90s, did you deploy to the Southwest Asia theater of operations? If so, there are a number of presumed conditions related to cancer and respiratory issues that are covered from there.

Aside from that, if you believe you have had toxic exposure, I suggest you contact your local VA's Environmental Health Coordinator (EHC)* and discuss next steps about being evaluated.
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* https://www.publichealth.va.gov/exposures/coordinators.asp