i think what the new (at least new to me) claim is that for the 19# injectors to work their best, it would be necessary to update the fuel pressure regulator so that our Pre-96 XJ's will have fuel pressure up to 43.5, rather than the 39 we are pushing now.
i've done a bit of reading and while there are varying ideas, i personally have been running the 19# on my 93' 4.0HO with no issue for the past 4 months (no amazing MPG gains to speak of, but my stock injectors were toast). I might toss on the new FPG next time i have 65$ laying around. But from the research i have just done (maybe someone else can correct me?), it looks like the up-graded FPG would be the best benefit at WOT.
The fuel pressure regulator is for 49 psi on the fuel rail at Wide open throttle. This will only be of benefit with 19# ev6 injectors. ev1 & ev1.3 injectors should be run at whatever pressure the fuel system they came from run at.
The 3 part numbers you can use are: Chrysler 4418850 or 5277829 or 5277864.- all 49PSI all will fit.
If you are a bit of a junk yard ferret -
Here is a list of cars that use this regulator:
CHRYSLER CONCORDE V6 3.5 F FI 1993-1995
CHRYSLER CONCORDE LX V6 3.5 F FI 1996-1997
CHRYSLER CONCORDE LXI V6 3.5 F FI 1996-1997
CHRYSLER DYNASTY V6 3.3 R FI 1991-1993
CHRYSLER IMPERIAL V6 3.3 R FI 1990-1991
CHRYSLER IMPERIAL V6 3.8 L FI 1991-1993
CHRYSLER INTREPID V6 3.5 F FI 1993-1997
CHRYSLER INTREPID ES V6 3.5 F FI 1995-1996
CHRYSLER LHS V6 3.5 F FI 1994-1997
CHRYSLER NEW YORKER V6 3.5 F FI 1994-1996
CHRYSLER NEW YORKER FIFTH AVENUE V6 3.3 R FI 1990-1993
CHRYSLER NEW YORKER FIFTH AVENUE V6 3.8 L FI 1991-1993
CHRYSLER NEW YORKER LANDAU V6 3.3 R FI 1990
CHRYSLER NEW YORKER SALON V6 3.3 R FI 1990-1993
CHRYSLER TC MASERATI V6 3.0 S FI 1990
CHRYSLER TOWN & COUNTRY V6 3.3 R FI 1990-1993
CHRYSLER TOWN & COUNTRY V6 3.8 L FI 1994-1995
DODGE CARAVAN V6 3.3 J FI 1994-1995
DODGE CARAVAN V6 3.3 R FI 1990-1995
DODGE CARAVAN C/V V6 3.3 J FI 1994-1995
DODGE CARAVAN C/V V6 3.3 R FI 1991-1992
DODGE CARAVAN ES V6 3.3 R FI 1993-1995
DODGE CARAVAN LE V6 3.3 R FI 1991-1995
DODGE CARAVAN SE V6 3.3 J FI 1994-1995
DODGE CARAVAN SE V6 3.3 R FI 1991-1995
DODGE DYNASTY V6 3.3 R FI 1990-1993
DODGE DYNASTY LE V6 3.3 R FI 1990-1993
DODGE GRAND CARAVAN ES V6 3.3 R FI 1993-1995
DODGE GRAND CARAVAN ES V6 3.8 L FI 1994-1995
DODGE GRAND CARAVAN LE V6 3.3 R FI 1990-1995
DODGE GRAND CARAVAN LE V6 3.8 L FI 1994-1995
DODGE GRAND CARAVAN SE V6 3.3 R FI 1990-1995
DODGE INTREPID V6 3.5 F FI 1993-1997
DODGE INTREPID ES V6 3.5 F FI 1993-1997
DODGE SPIRIT L4 2.5 V FI 1994
EAGLE VISION ESI V6 3.5 F FI 1995-1997
EAGLE VISION TSI V6 3.5 F FI 1993-1997
PLYMOUTH ACCLAIM L4 2.5 V FI 1994
PLYMOUTH GRAND VOYAGER LE V6 3.3 R FI 1990-1995
PLYMOUTH GRAND VOYAGER LE V6 3.8 L FI 1994-1995
PLYMOUTH GRAND VOYAGER SE V6 3.3 R FI 1990-1994
PLYMOUTH GRAND VOYAGER SE V6 3.8 L FI 1995
PLYMOUTH PROWLER V6 3.5 F FI 1997
PLYMOUTH VOYAGER V6 3.3 J FI 1994-1995
PLYMOUTH VOYAGER V6 3.3 R FI 1995
PLYMOUTH VOYAGER LE V6 3.3 R FI 1991-1995
PLYMOUTH VOYAGER LX V6 3.3 R FI 1994
PLYMOUTH VOYAGER SE V6 3.3 J FI 1994
PLYMOUTH VOYAGER SE V6 3.3 R FI 1991-1995
All this info is here:
http://www.cherokeeforum.com/f2/more-budget-injector-upgrade-questions-13848/index3/
With a synopsis here:
http://www.ausjeepoffroad.com/forum/showthread.php?t=92236