200sx se-r hesitation gremlin

[moso]

i posted this over in the sentra forum but i thought i might get better results here. so here goes.

i have a 95 200sx se-r with the sr20de 5 speed she has 150k and for the most part runs like a champ. i just bought this car in september and my girlfriend has been driving it. here is the problem. when you blip the throttle it stumbles just off idle before picking up rpms and occasionally while idleing it will miss once. and i mean occasionally like once out of three times sitting through a full cycle of a city light. i have checked and/or adjusted and/or replaced the following

MAF - new - excelent groundTPS - new- .052vIACV - cleaned and adjusted - base idle 680rpmsTiming - adjusted - 16btdcfull tune up including NGK plugs and oem wires cap and rotornew fuel filternew air filter (K&N Filtercharger)consult cable used to check for codes - none present - all sensors functioning normallyreplaced all vacuum lines and cleaned metal line under BPT valve.

now i have no idea of what condition the fuel pump or fuel pressure regulator are in and i know i need to change the timing chain which is slated to be done just after xmas. what is it im missing? any help is appriciated.