Wow, not much left to diagnose. I'd get some propane and check for vacuum leaks around the lines and throttle body. If you're losing power going uphill the only thing that comes to mind is the vehicle speed sensor. That can affect accelerating uphill. If it's blocked with metal filings then it won't know what gear to be in.


Do you smell fuel? Any water / fuel / carbon out of the exhaust? Have you cleaned your TB with TB cleaner? changed PCV? Changed air filter? Changed the fuel filter?

 

fuel pressure is not bad, i think 3.8 has a tad higher pressure. might be time to get her hooked up to a good scope and or scanner and see what numbers dont look good.

 

Got an update for you all. Since last reporting and eliminating fuel delivery as a suspect (pressure good, regulator good, pump good, new fuel filter, cleaned and flow tested injectors) I bought 3 new AcDelco D555 coils to completely eliminate ignition (new wires, plugs, coils, ICM). Air appears to check out too (good vacuum, good compression test, no RPM bump with the propane torch leak test). All I have left if maybe a timing issue (camshaft position sensor or another sensor) and a exhaust restriction. Since testing exhaust back pressure is easier and the more likely suspect I rented a back pressure gauge from Autozone. So far I've only tested from the driver side upstream O2 bung and ran out of time today to test the passenger side. From the driver side pressure at idle is below 0 PSI and holding at 2500 RPM is between 1.25 and 2.5 PSI which both sound good to me (also within the green range on the gauge haha). Upon pulling the driver side O2 sensor (original sensor) it has a heavy tan buildup in a spot on one side and the rest of the sensor tip looks like it's coated with something that almost looks like anti seize and is completely covering some vents. Attached are pics, what do you guys think? Pretty sure I'm going to order a couple upstream O2 sensors.

 

did you put new headers on? looks like something is in the exhaust, can see specks of something on it.

 

No headers, still the original exhaust manifolds. You're right craby, it does look like there's specks of something on it (the tan spot has almost the texture of sand).

 

Have you been losing any coolant? One cause of the light color buildup can be from antifreeze contamination. The dark side looks like you're burning rich.

 

did you check all the plugs, may have one thats getting ate up.

 

i was wondering if coolant would do that. what about water in gas

 

Water in the gas would turn to steam in the cylinder. If anything, I'd expect that to have a cleaning effect. Water or water/alcohol injection on turbo cars isn't all that uncommon, and I'm not aware of that having adverse effects on the O2 sensors.

 

All the plugs looked good when I pulled them (light brown/gray) but they were also only about 6 months old. Haven't had coolant leaks for about 9 months now. Had to replace the radiator in January because of a hairline crack on one of the tank to hose connections. But that also brings up a good point, I haven't checked the coolant level for probably about 3 months now. Sure hope I'm not burning coolant because I haven't seen any leaks. Funny thing you mentioned water in the gas. Right around the time this started happening I also started putting in Shell gas. I'm certain it's just a coincidence but when I told my exhaust guy this he said that Shell had some issues a while ago about their gas causing pinging, not sure how valid that is though.