Simpsons sleuths take heart. On Sept. 17, there will be a satisfying conclusion to the ''Who Shot Mr. Burns?'' mystery. Or so says Simpsons creator Matt Groening: ''It's not going to be a big disappointment, like 'Who Killed Laura Palmer?''' Fans have been on the case all summer, sifting through endless speculation on an Internet newsgroup (alt. tv.simpsons) and a Who Shot Mr. Burns? World Wide Web site (http://main.springfield.com) amid, ay caramba!, red herrings galore. Not even mambo king Tito Puente, a season-finale guest star, has escaped suspicion. Some hotly debated cliff-hanger clues:
1. A wounded Mr. Burns falls over the Town Hall sundial with his arms pointing toward S and W (or M), but many characters share these initials (Waylon Smithers, W. Seymour Skinner, Maggie Simpson, and Side show Mel, to name a few). As Smithers says, ''The town's sundial will be useless.''
2. Several clocks in the episode read 3 o'clock. Executive producer David Mirkin confirms that ''time plays a part.'' That may clear Smithers, who claims he never misses Pardon My Zinger, which airs at that time.
3. After Grandpa Simpson whips out a loaded Smith & Wesson and hands it to Bart, Marge buries it in a cigar box which later turns up empty. This could implicate Marge but seems too obvious to be a legitimate clue.
4. Standing before a sign painted on the pavement, Homer blocks all but the letters N and O and an arrow pointing at him. Even so, ''Homer becomes a big suspect,'' says Mirkin. ''That's a big piece of information.''
5. Burns' holster is empty as he collapses onto the sundial. Net-heads think his missing gun will play an indirect role in the solution.
6. When Burns strikes oil, he raises his arms in a triumphant Y gesture, which combines with the E and S of the Moe's Tavern sign in the background suggesting that Burns is the culprit, accidentally shooting himself. But, Mirkin warns, ''people have seen things that weren't put there intentionally.''
All well and good. But what about ... Tito Puente? Mirkin hesitates. ''It wouldn't be out of the realm of mystery writing to have a guest that wound up being ... ummmm ... I won't make a judgment call on that, one way or another.'' Tito, call your lawyer.
Gary Eng Walk, with additional reporting by Jason Kaufman