I performed the compression test twice on all four cylinders (got the same results) then i added oil to cylinder 4 and tested it one last time. The consistency tells me the fitting was properly installed.

I'm not sure if further testing is necessary - repairing anything that may have caused the low compression is going to be either too costly or too time consuming if i do it myself. What do you think?

 

Did the engine run normally prior to quitting? If it ran not were there any signs of problems just prior to quitting?

Did the engine ever overheat?

Was there any oil on the dipstick when you checked it?

Low compression is going to cause issues regardless of how it got that low. Assume no easy fix for this issue and it would be expensive if not DIY on repairs.

 

Prior to the engine quitting, these were the symptoms:
1- the idle was rough. it was jumping over and under the 1k RPM. turning on the AC or heat would almost stall the vehicle so i never used it
2- there were many codes when i got the car (P0300, P0301, P0302, P0303, P0304, P0141, P1135). I cleared these codes and drove the car for a bit to see what the first codes were going to be, they were (P0304, P0171, P1130)
3- this is when i started to replace parts on the vehicle like camshaft position sensor, battery, fuel pump, spark plugs, spark plug wires

Engine never over heated and dash never displayed low oil (even though it was BONE dry when i checked after it died on me)

 

A lot of these codes are related the air/fuel mixture. It could be a bad A/F sensor is causing the engine to run too lean. You stated you checked for air leaks in the intake air system.

Other codes are related to various cylinders having a misfire. Would suspect if No 4 low compression was the only issue then the codes would point to No 4 only and not all cylinders.

It happens on this engine the oil pump drive shift seal leaks and causes a good deal of oil lose.

Research each trouble code on the internet to find the common theme as say the bad A/F sensor.