Beyond what you have done already the only other avenue is a PC 851.8 petition for factual innocence which if granted results in your record being sealed and eventually destroyed. Of course you would have major obstacles to overcome since you were convicted, not to mention the lapse of 22 years. You have nothing to lose in taking a shot however; a lawyer would enhance your chances.
A defendant's court record is not expunged or sealed when Penal Code 1203.4 (commonly, and probably inappropriately, referred to as an expungement) relief is granted. Instead, an extra entry, "dismissed, is made on the record. The court file remains a fully public document.
I respectfully disagree with Mr. Kaman on this. If you were convicted by a plea or jury, you have virtually no chance at all of a finding of factual innocence. You say you were "convicted" and are not professing your factual innocence.
You're now dealing with the federal government, which wouldn't give a hoot anyway as to what a state court might do. The SENTRI program could recognize the state conviction under any circumstances, as the federal government is not bound by state court actions. So, whomever in SENTRI asked you to "clean" that conviction may have been blowing smoke your way.