I have a 1998 lesabre with 140,000 miles, the other day it died and would not start. I changed the fuel filter and it started but ran like crap I had to pump the accelerator to get it to run and would die if I pressed it to hard like anything pass half throttle while driving. When setting in park in the driveway if I push the pedal too far down it would hesitate and then rev up while letting off the pedal but I had to hold it down a little to keep it running. I noticed a coolant leak around the upper manifold and replaced that and new gasket. Ran the same hesitates and try'* to die while driving. When parked it will run by its self only after I have spent some time pushing the pedal down repeatedly and quickly. While in park I can rev the engine as much and as high as I want with a slight hesitation. While driving if I rev pass 1/4 or 3/8 pedal it tries to die. I had 6 different codes before I replaced the map sensor and manifold. Now I have 2 but it runs the same. P1665 and P0102. I was thinking it might be a vacuum leak but I have not been able to find one. Anything thing I can do to figure out what'* going on without just throwing parts at it or anyone have an idea what'* going on? Thanks in advance and any advise and or help would be awesome.

With it throwing a MAF related code, you can often unplug the MAF sensor to see what happens. The engine will either run completely differently but better, or it will get worse.

Have you checked any other vitals such as fuel pressure? Have you also confirmed the Fuel pressure regulator isn't leaking in to the intake? You can pull the vacuum line off of it while running, and if fuel comes out, you have problem.