Van Running Lean under acceleration

[Aqua Angel]

I have been reading a lot of your posts and others and i still can't find the issues that i have here.

I have went above and beyond this van as i babysit this beast to be the best, but lately, it has not been helping me at all.

I have had the SES light lit on my dash for a while to find out that my EGR valve was gone. So i have replaced it with many other things with it and hoping that it would solve this Lean running condition to go away and it hasn't.

i have replaced the following:
EGR valve
EGR solenoid
map sensor
Tps sensor replaced
several vacuum hose
O2 sensor
Spark plug replaced
distributor cap replaced and so as the rotor
Ignition module replaced
redone the exhaust
rebuild the Fuel pressure regulator
my temp sensor was replaced 3 months ago and so as my fuel pump

i have custom "Handcraft it myself" seals for the "Tin section of the tbi area" as none of the store had the lower nor the upper seal for the humm how do you call it? where the vacuum hose connect to the valve cover on the driver side.
And the van still runs Lean when i go up the hill or when i step on the gas.
City driving is fine, but highway? the gauge stays in Lean all the way until i release the gas pedal or i stop at a traffic light.

i do hear a vacuum leak, but i can't locate it. i have tried the brake clean spray and the engine has not changed it's RPM.

Could there be an internal vacuum leak in within' the TBI area "meaning tbi to air intake gasket"

That is the only place which i haven't touched. the leaks seems to be coming from the driver side. hoping that won't be the brake booster leaking. the tranny does shift kind of hard at some times, but not often.

So we are working here on a Chevy Astro van 93. engine code "Z"

If anyone could help before i go back to work with it to make it run the way it should.

Cheers and many thanks for those that can help me out.

[Blue Bowtie]

Clamp off the brake booster vacuum line and see what happens. There will be no power assist for the brakes, of course, so stopping will require a LOT of pedal effort. Your other option is to insert a fitting with a small orifice into the brake booster line so that it receives some vacuum to empty the reservoir, but cannot leak enough to appreciably affect mixture.

[Aqua Angel]

Well what do you know.

The van is running like a dream, better than the day i first bought it. everything was replaced as mentioned previously except that one of those new item was faulty.
My new O2 sensor was Shot making the van to run lean, so much for a brand new part. i put my old one in there and ran SUPERB, But it is still contaminated, so i will have to have a replacement. so lesson learned. don't throw your old parts out to the trash until you get your results. New parts can be faulty.