Re: Pearly Gates in Les Paul won't get lasting harmonics?? What is up here???
Pearly Gates will be divine in any normal guitar, they go with anything from maple-necked fenders to mahogany gibsons. Awesome stuff. I'd suspect blame your guitar, not the Pearlies.
ESPECIALLY since you mentioned "strings squeal a couple seconds" acoustically right? Well, I'm sorry to say that in a light-bodied, bolt-on, lower-mid-tier MIJ that I'd scored for 95 bucks, I get about 13-15 seconds sustain acoustically... On some better guitars, when set up properly etc., it can go 20+. Guitars are supposed to resonate. Soo, either your pups are SOOO up there that the mag pull is killing your strings, like others said, or your guitar's construction is a sound-muffling mess... Me, I'd think you'd feel the mag pull and notice what's up when trying to play, and Pearlies don't exactly have superheavy magnets, either... if you really believe it's not the guitar and wanna get to the bottom of it, REMOVE the other pup entirely (don't just unsolder, also PHYSICALLY pull it out or at least lower it as far as it goes), and solder the Pearly alone STRAIGHT TO YOUR INPUT JACK, no pots no switch no nothing (in 2-conductor mode, like a Gibson pickup, a hot and a ground... google or read the manual or ask here about which wires to twist off tape off and/or solder together to get a 2-conductor out of the 4 I'm guessing Pearlies come with these days). See how it acts from there. And, if the premise just terrified you, toss that 15-30 watt pencil you're probably using and get a 130 watt soldering tool w/ pistol grip (best $19.99 you'll have spent in years), suddenly soldering two points to a jack will seem like child's play and not a pain you're reluctant to start messing with. Anyways, if Pearly wired up straight and alone still sounds the same, it's anyone's guess, but if it starts performing as usual, it's somewhere in the pots or the other pickup or a cold solder joint you've got, etc.
But, sorry man, but I'm gonna have to go with:
"Duh, prolly just it being an EPI, dude".
...maybe you've owned an MIJ elitist in the past, or missed the redistribution of cheapo-but-serviceable guitars back to America as the "faded" "melody maker" etc. Gibson series, while most all of Epi's current lineup is an UNSERVICEABLE, EXPENSIVE variation on the Fotoflame on Plywood/Veneer on plywood/Acidic bright modern pain on plywood/and thick matte non-transparent on plywood... OR WORSE. After all, GIBSON USA's been seen flogging PRESSED CARDBOARD FINGERBOARDS, so what can we expect here? Pressed phonebook fingerboards? Toilet paper? Dunno, but just when you'd think, no way it couldn't get worse, it DOES.
Even the 3-super-distortion Ace Frehley sig with the decent neck and seemingly cool woods somehow manages to sound DEAD. They're super distortions, for Xenu's sake, how can you possibly bugger that up so hard they don't crunch up? Dunno. But they managed.
Next up, expect super low output EMG81s. And reclaimed toilet paper in the specs.