So after much testing and looking up stuff online I have repaired:
- Exhaust manifold ( was cracked but I welded it and now has no leaks)
- Fuel pressure regulator
- O2 sensor
- EGR pipe
- Fuel filter
- Fuel pump
- vacuum lines
- Replaced all spark plugs
- Replace distributer and cap
- replaced plug wires
- Three injectors are from new, but for a corvette, three are original, the new ones registered an OHM reading of 15ohm, and the old ones registered 16-17ohms

Currently the symptoms that I am experiencing are:
- long and hard start-up time (takes about 4-6 cranks and sounds like the starter is having a really hard time turning the engine over)
- lack of power at high speeds (highway etc)
extremely bad fuel mileage (getting about 9-10 mpg)
- gassy smell at all times which is so strong I smell it in the interior (smells like partially burnt gas, not raw un-burnt gas)
- AC defaults to defrost when climbing a hill, or when accelerating past 2500rpm
- rough idle in a cycle, it idles up and down from 800rpm - 200rpm very predictably in a cycle every 8-10 seconds

I'm pretty sure that all the vacuum lines go to the right places, and I am positive that there are no leaks in the lines themselves, the map sensor still works fine, I tested it, the O2 sensor is new, the tps still works fine, tested it as well, and IAC is really clean so I don't think it's the problem either, the whole throttle body is clean and doesn't stick, I seafoamed it once before, seemed to clean it up a lot but didn't change much, I also replaced all the spark plugs It seems to RUN fine, but just uses waaay too much gas, that's really the only thing I am concerned about, so if you guys have any ideas as to what could be causing this, that would be great, cause I'm stumped

 

Click on the link in my signature. Start with post #1.

 

if its defaulting to defrost that sounds like a vacuum problem.

 

The mix and match of the injectors is worrisome.

 

I Re routed some vacuum lines, it seemed to run better, but now I have no A/C, just defrost. I will have to take another look at that, but the reason it was taking so long to start was just the wire that runs from the battery to the starter, it was rusted and broken, barely making contact. I replaced it and it starts fine now, but its still uses a ton of gas.

 

Uh-hum. Three Corvette injectors in there?

I wonder if their flow rate could be just a smidgeon higher than an old Renix injector when given the same pulse width?

There's an elephant in the room and you're not seeing it.

 

Agreed.
The LT1 Corvette injectors have a higher flow rate and different spray pattern than the stock 4.0 injectors. That's why I have them in my 4.9.

To the OP, try using all 6 of only one style injector. This will help take care of some issues. Then after that, we might be able to help you better diagnose this.

 

Thank you for clarifying this. "I've got a mish mash of **** cobbled together and can't figure out why it's not working".

 

Listen to them my buddy. Itll save you some headache and def do Cruisers renix tips.

 

So I decided to go 4x4ing when I probably should have been working on it...

Anyway, I have a snorkel installed on it, something that I built at home using 2" PVC pipe, never had a problem with it on-road, but it started acting funny after a few hours of driving around off road, so I shut it off and checked different things, I ended up opening the air box only to find it dripping wet with engine oil, so somehow it was syphoning oil back through the intake manifold to the airbox. I didn't even think this could be possible.
what could cause that?

 

https://www.cherokeeforum.com/f2/88-...air-box-66801/
Couple of things to check in there...

I agree with them though- Running different injectors can't be doing it any good.

 

2" is not enough air flow. 3" or larger.

 

Not only the things above, but those Vette injectors are probably washing the oil off the cylinder walls thinning it out.
Does the dipstick smell like raw gas?

 

I have just learned that the injectors that were put in were not corvette injectors, so I have no idea what they are, but they have a larger broader end with a wider hole, indicating a different spray pattern and higher flow rate. The thing that gets me though, is that it used to work fine with the same injectors, getting upwards of 500k per tank, then it sat for 4 years and now it gets less then 250k a tank.

Also, yes, the oil smelled a bit gasy when I checked it.

Plus, the three original injectors have a OHM reading of 16-18, is that normal?

 

Don't know about your year, on OBD-II it's 12 ohms +/- 10%. I would change everything to the correct injectors for your application.

Just for fun, can you provide is the part numbers off the the current injectors? They're written on the side.