What do you mean:Checked fuel pressure which is showing some signs of being erratic
What is the pressure?
Toggled EGR and no change with a Tech I? This a linear , electrical EGR? If yes, and car did not fall on it's face as you opened it? If so, sounds like the upper plenum may be plugged, or the tube to the EGR is pugged or the EGR is not working.....this should have set a code....
You replaced the spark plugs....did one plug look different compared to others? Did you use OEM plugs? Did you change the wires? Did you check the coil terminals for carbonning or arcing? Did you check coil output with a spark tester?
Are you losing coolant?
Have you checked vac line to F/P regulator for the presense of gas?
Have you checked for vac leaks around the engine with carb cleaner?
Are there any codes?