Volvo: Volvo 940 wagon , sluggish acceleration after traffic driving, fuel pressure gauge, volvo 940 wagon

Question
Hello, I have a '93 volvo 940 wagon with 130,000 miles in mint condition,
except for a leaking a/c condenser that I have yet to fix as summer is not
upon us quite yet.
Recently it has the following behavior: After an hour or so of stop and go
traffic driving (in the city) - from a complete stop , at a stop light, when I
press the gas pedal, it does not want to accelerate/respond and feels like it is
in 2nd gear as it moves foward. If I floor the pedal and after about 5 seconds
it "kicks" in and seems to be accelerating and shifting normal then it is
normal while driving. Only after a complete stop or coasting at idle before
acceleration does this occur. Also, It does not seem to occur at all during or
after driving on the highway for a period of time only after stop and go
driving. The temperature is normal and all cooling systems are functioning
normally in all cases. I ran some fuel injector cleaner through the tank
recently just as maintenance although this was happening before the cleaner
was run through.  I am afraid of my mechanic changing several parts that
don't need it to try and find out the problem. Any thoughts where to have
him check first? Thanks, Eric NYC.

Answer
Eric,
Read the codes in the fuel and ignition system follow those. Make sure that the in tank pump is working (if you have the Bosch system).
With a fuel pressure gauge attached see if the fuel pressure fails when the lose of power happens. If it fails you will be looking at fuel pump or pressure regulator.