Hey everyone!
First post here. I have quite the issue with my 2005 MCS that I just got recently, hopefully I can sum everything up rather effectively.

Vehicle details:
2005 MCS. Base base base model. Cloth seats, slicc top, manual trans, no cruise, etc.
210,xxx miles.
Have owned it since 6/29. Bought it with the issue I am currently experiencing.

Previous owner's work:
Replaced throttle body
Replaced throttle pedal
Changed multiple sensors to new OEM (owner before him had lots of amazon stuff on the car)
Fixed some wiring that had been gnawed, but not chewed through
Said it ran great once or twice, but otherwise has always been the same

My work:
Replaced primary O2 sensor with NTK unit
Replaced spark plugs with NGK BKR6EQUP
Replaced ignition coil
Replaced spark plug wires
Replaced coolant temp sensor
Replaced battery
Replaced battery ground cable

Current CEL(s):
Coolant Temp Sensor p0118 (i believe a connector or wiring issue)
B1S2 O2 sensor (unplugged due to a short somewhere in the wiring, which was popping the f3 fuse)

The issue(s):
The car will not drive normally once the throttle is depressed more than around 30% or so. It starts to buck a ton, barely accelerates/climbs revs, and is pretty sad. Below that throttle threshold, you wouldn't think anything of it. I do have an issue where the first cold start the car will die, then after that it will idle just fine.
After replacing the parts I have, the car now CAN freely rev, but I still have the same issue once it is under load. Using a Carista OBD dongle, I have don't some live data recording, and everything *appears* to be normal. LTFT and STFT at WOT both look good, the app registers 155kPa for intake mani pressure, which converting to PSI and taking out atmospheric should end up at around 8psi at 4200 RPM.
Timing is the one number that semi-concerned me, being 26* in one pull I recorded, and I saw it as high as 28* in other ones. I do not see any reason why this car should have 28* of timing in it at 4200 RPM, unless it is HEAVILY compensating for something. Outside of that, the car has oil, coolant, gas, etc. Gas should be less than about 6-8 months old, and was known good 93 at the time. No codes other than the coolant temp sensor and the unplugged s2 o2 sensor.
Does ANYONE have any ideas where I can look next? I would have though MAP or TMAP if I was throwing a code, but I am not. I tried zip tie-ing the BPV, no help there. I will say that the plugs and wires made the car a bit better, but it still is nowhere near normal.
I did also today start getting some pops on decel and when revving stationary and letting the revs fall back down. First time I have ever heard that, and that was after plugs and wires.

Could I possibly have a timing issue? Boost leak? Supercharger problem? Fuel pump?
I have a NIB fuel filter I can throw into the car, but I seriously doubt that a fuel filter would cause THIS much of an issue.

Any help is massively appreciated.

Thank you!

 

Not sure if the 2005 had the standard "pops and crackles" tune. My 2003 does not. Does it sound like "normal" pops and crackles or is it louder, like a backfire?

Maybe do a compression test. If compression is normal, you could rule out the engine being out of time.

 

I would say they sound like normal overrun, but it is quite a bit. PO said compression was strong on all cylinders, and after checking all the plugs from a bit of driving, none of them look worse than another. I’m inclined to believe him.
Could the crank pulley cause any of this?

 

Fixed with a fuel pump.