You could do a simple shade tree test of the fuel rail. If it is leaking then it will not hold pressure. Let it sit for a couple of hours. Pull the cap off the test port. Take an old tire pressure gauge, wrap a rag around it and press the schrader valve. You should get a nice strong blast of gasoline (which is why the rag is important). If you don't then you have a leak somewhere. My guess is that if you took it to a shop that they have already done a pressure test.

 

I was in the shop bay when they opened the hood. They didn't do a pressure test. The guy just looked around with a flashlight. No I didn't pay for his diagnostic either. He didn't open anything. He said that an advanced diagnostic would cost 60 bucks. Ha. I get DF advanced diagnostics for free. Anyway, I bought a fuel pressure tester from www.carparts.com. It should be here by the end of the week.

 

Check the entire fuel line for integrity.
If the guy didn't do a pressure test and just looked under the hood, that is worthless.
Depending on where you live, the fuel and brake lines in these 2nd gens are typically in various degrees of decomposition.
Heres a shot of mine a couple months ago, while replacing a ruptured brake line
https://dodgeforum.com/forum/1790691-post19.html
Still some life in it, I'm hoping for a couple more years.

They don't always necessarily rupture and fail dramatically, I could be something progressive, just allowing a little leak. If thats the case, its a matter of time before it blows through. Both lines tend to be the worse when they get between the gas tank and frame rail, where you can't see them.
If the leak is there, you'd have to go by hopefully finding a drip, or smell.

Just another possibility, along with the others suggested.

 

Ok. So I did a fuel pressure test and my fuel system is holding at 49lbs. I took off the throttle body and I saw a little oil in the intake. I got a few quotes on replacing the plenum gasket and pan. Just the labor on the cheapest quote is $435. That's $87/hr for 5 hours. Is this a good price? Seems steep to me. How hard is this to do my self?

 

I doubt the pan will be replaced with a Hughes or APS unless you provide it for them. You'll have the same problem if you don't replace the plate. As far as doing it yourself goes, get a manual, read the whole removal/install procedure. If you have the right tools, cleaning supplies and desire, it will take you a weekend to do it without rushing and doing it right.

And btw, the front o2 sensor and the cat are probably shot or not too far behind.

 

I just bought the Magnafow direct fit cat and a new Magnaflow muffler. I am buying both new o2 sensors and new headers (i just want new headers) for after the plenum fix is done. Can someone help me with some links to DIYs or some where to buy/download a good manual with the procedure?