I post this question before, and did not receive much feedback.
I never fill up with 89 or higher octane gas, always with 87 for my '95 Merc Mystique 2.5L ATX. I don't think the car requires higher octane, and I am cheap

. Perhaps I try 89 gas to see if it fixes the occasional gas smell in mine?
The fuel smell usually happens after a cold start, after some short distance driving, mostly experienced in during colder months, when the window is mostly closed (?). It also happens after some spirited driving, reads: WOT, any other time of the year.
I had a Ford mechanic replaced all the injectors cone-shape O-rings. Although some old O-rings looks deformed, replacing with new O-rings did not fixed the problem.
Today's local paper printed a reply from a Ford engine mechanic about a possible leakage at the contoured fuel filler neck, that may produce the raw fuel smell. This one is new and may not be the cause. However, it is worth mentioning.
Dave