2L JTS Rough Idle

[Dr_Doom]

Hi, my 2L JTS has a rough idle and a bad exhaust smell. It misfires a bit on idle with the rpm needle fluctuating but no engine light. No engine codes are showing recently, but sometimes it would show a general misfire code and cylinder 1 misfire on MultiECU Scan, but no engine light. I pulled the plugs out and all were a bit black and sooty, but not wet. A compression test showed that cylinders 1,2,4 at 150psi, but 3 at 125psi, a bit of oil in the cylinder and compression increased to about 200psi but the plug looks the same as the rest (not more sooty or wet/oily). There is also no major/large amounts of smoke coming from the exhaust. I was thinking if maybe all 4 injectors are letting too  much fuel in but I want to see if anyone else has any other ideas of possible causes.

Is it possible that a previous owner tuned the ECU to run rich? (ECU looks stock) Or maybe an incorrect reading from a faulty sensor changing the fuel mixture? I have added fuel injector cleaner to try and see if anything changes but same result.

Any insight would be greatly appreciated.