I have a 92 ford f 250 with some trouble codes 334 172 536 Can't figure out what the problem is let me tell you a little history about the truck the truck has 205,000 miles it originally had a natural gas system that has been completely pulled out of the truck ...things I have replaced in the last few weeks have been spark plugs spark plug wires cap rotor idle air control valve throttle position sensor EGR valve EGR valve sensor Truck gets horrible gas knowledge about 9 miles to the gallon I have checked for vacuum leaks but can't seem to find any any help would be very appreciated

 

The 536 code is just that someone forgot to cycle the brake pedal when doing a test.
The 172 code may involve the oxygen sensor which could be stuck lean.
The 334 code is related to the EGR system and it could be the replacement position sensor may have a problem or the wiring from it may be open.

 

How much vacuum suction is supposed to be going to the EGR valve from the green hose because it seems like it's just vibrating when I put my finger over it

 

You can remove that vacuum hose , plug it, and see if it makes any difference.Also , give the EGR valve a few light taps to dislodge any carbon that might be stuck in it.
You might remove the valve to check if it closes completely.

 

EGR valve and the EVP sensor are both brand new just replaced him

 

With the older vehicles the only way to confirm oxygen sensor operation was to either create a big vacuum leak to force it to go lean or to enrichen the mixture with propane or additional fuel to force it to go rich and confirm that it did respond.
Are you able to do this so the sensor operation can be verified and eliminated from the check out?
Just a side note, not to cause you addl grief, but lately so many replacement parts have been installed that were defective right out of the box, not very encouraging.
That is why we need to be sure of a diagnosis with testing and knowledge of system operation and not rely entirely on "expected good new parts" that are JUNK !
If you understand how the system works , perform the correct tests and it points to a particular incorrect result and you are sure a part is malfunctioning , it doesn't matter if it is new , if it doesn't work correctly, it's NO Good. Very common problem these days.

 

I was getting a l lean code and a rich code at the same time then I fix some things reset the battery and the Rich code never came back on

 

If to the best of your knowledge the O2 sensor has never been replaced with those miles chances are pretty good it is time to replace it . If at all possible use a Ford sensor,Motorcraft . Don't necessarily have to get it from a dealer.

 

It definitely is the original one just pulled it off it says ford and Bosch right on it