LESS THAN STANDARD SEPARATION BETWEEN COMMUTER AND ACR ACFT ON FINAL APCH. OPERATIONAL ERROR.

Narrative

WHILE OPERATING COMMUTER X INTO IAH ON AN IFR FLT; WE WERE HANDED OFF FROM A DOWNWIND POS TO A SECOND APCH CTL SECTOR FOR RADAR VECTORS TO THE FINAL APCH COURSE. ALL PROCS AND HANDLING BY ATC WERE NORMAL UNTIL TURNING TO THE INTERCEPT HDG FOR THE ILS 14L. AT THAT TIME OUR POS WAS APPROX 5 MI FROM THE OM AND WE HEARD APCH CTL REQUEST ACR Y BEHIND US; ACFT TYPE UNKNOWN; TO REDUCE SPD. ACR Y REPLIED THAT HE WAS 'TRYING TO GET DOWN' RIGHT NOW AND COULD NOT SLOW UNTIL HE REACHED ASSIGNED ALT. APCH CTLR THEN REQUESTED MY FLT TO INCREASE SPD 'IF FEASIBLE TO 230 KTS UNTIL FURTHER ADVISED.' WE VOLUNTARILY COMPLIED WITH THE REQUEST AND THEN WERE INSTRUCTED TO 'DELETE THE SPD RESTRICTION AND CONTACT TWR' JUST PRIOR TO XING THE OM. WHILE SWITCHING TO TWR FREQ AND DECELERATING TO CONFIGURE FOR LNDG; WE TRANSITIONED FROM IMC TO VMC AND OBSERVED THAT WE WERE ON THE SAME GLIDE PATH AND 1-1 1/2 MI BEHIND ACR Z AND CLOSING. I ADVISED THE TWR THAT WE HAD THE RWY AND THE TFC AHEAD IN SIGHT; AT THE SAME TIME MANEUVERING SLIGHTLY TO THE SIDE OF THE LOC TO AVOID THE WAKE OF LGT Z. TWR ASKED IF WE COULD ACCEPT THE SHORTER PARALLEL RWY 14R AND WE WERE CLRED TO SIDE STEP AND LAND ON THAT RWY. THIS SITUATION SEEMED TO HAVE BEEN CAUSED BY A LAPSE OF COORD BTWN CTLRS IN WHAT IS NORMALLY A VERY GOOD SYS AT IAH. ALTHOUGH I WAS AWARE OF ONLY THE POSITIONS OF MY OWN AND THE FLTS IMMEDIATELY AHEAD AND BEHIND ME AND NOT THE OVERALL TFC SITUATION; IT WOULD HAVE SEEMED SAFER TO VECTOR THE FASTER DSNDING ACFT BEHIND US RATHER THAN ACCELERATING AN ACFT NEARING THE FINAL APCH FIX READY TO BE HANDED OFF TO THE TWR.