i'm going to try to help (with an emphases on "try")
I think the part your talking about is called the "FUEL PRESS RLF VALVE"
mind you this is for a 97, was called the same thing for a 95, but changed on 96's (i'm guessing fuel line recall)
and with new steel rails (recall fix) is no longer needed
and caped off like mine!
(sorry about the pic quality but it was COLD outside)now i'm going to try to confuse you............LOL
and listed as part 547 in the diagram, for a 95
at this site it states... "(WHEN REPLACING MANIFOLD, CUSTOMER MAY NEED TO REPLACE THE PRESSURE REGULATOR VACUUM TUBE W/12558023 & CAP OFF PORTS WITH NEW MANIFOLD USING CAPS)" as does RockAuto (where i got the part # for the intake!
i hunted down part #12558023 and came up with:
www.compnine.com/index.php?name=12558023said price was $6.43.
but when i go to the diagram for a 97
i get a price of $35.69 for the same part, and states
"VALVE,FUEL PRESS RLF(PART OF 534 intake)"
www.compnine.com/index.php?u=1&year=1997&artnbr=3M00-015&artsfx=NULL&supplgroup=80&catcode=35G&modelcode=G&makecode=O&modelseries=GA&uid=1&modelid=1147577364&capuid=1&majorgroup=00&grouptype=Bi'm really not sure if you can buy this part separate from the intake, i can't find it at any GM parts source other then this one!
sorry! you may want to get intouch with them.
some options for ya, might be if you can't find the part:
A two part epoxy to seal the leak (as this part is no longer needed,with the fuel rail fix and is just caped off)
A new intake $279.79 from rockauto (forget that)!
or a bone yard part?
the whole intake for your 95 will interchange with these:
Aurora 1995-1995 G(L47)
Aurora 1996-1997 G(L47)
Aurora 1998-1999 G(L47)
Concours 1995-1995 E(LD8,L37)
Concours 1995-1995 K(LD8,L37)
Concours 1996-1997 E
Concours 1996-1997 K
Concours 1998-1999 E
Concours 1998-1999 K
D'Elegance 1998-1999 E
D'Elegance 1998-1999 K
Deville 1995-1995 E(LD8,L37)
Deville 1995-1995 K(LD8,L37)
Deville 1996-1997 E
Deville 1996-1997 K
Deville 1998-1999 E
Deville 1998-1999 K
Eldorado 1995-1995 E(LD8,L37)
Eldorado 1995-1995 K(LD8,L37)
Eldorado 1996-1997 E
Eldorado 1996-1997 K
Eldorado 1998-1999 E
Eldorado 1998-1999 K
Eldorado Touring 1995-1995 E(LD8,L37)
Eldorado Touring 1995-1995 K(LD8,L37)
Eldorado Touring 1996-1997 E
Eldorado Touring 1996-1997 K
Eldorado Touring 1998-1999 E
Eldorado Touring 1998-1999 K
Hearse 1998-1999 E
Hearse 1998-1999 K
Limousine 1998-1999 E
Limousine 1998-1999 K
Seville 1995-1995 E(LD8,L37)
Seville 1995-1995 K(LD8,L37)
Seville 1996-1997 E
Seville 1996-1997 K
Seville 1998-1999 E
Seville 1998-1999 K
well good luck, if you go for a bone yard part, and can't find one pm me.
i'm sure i can come up with one, for part cost+shipping