Noise and low engine power

I just bought a fairly used car listed above 2011-2012 model. When I took it for a test drive, I heard noise when I accelerate which then smooths out as I drive on until I brake again and try to accelerate, this noise seems to be coming from under the hood on the passenger side. I bought the car regardless thinking it could be exhaust issues and traveled with it. The sound continued all through the nine hours travel but no new issue developed and I seem to get good gas mileage. The next morning I honestly did not do oil checks before takeoff, I had hardly driven for five minutes when low oil pressure light came on, I packed almost immediately less than 300 m after, bought a liter Total oil (20W) and added approx. 0.5ltr which turned out to put the oil at over-gauge, the low oil pressure light went off anyways, even though I didn’t try to run or drive the car any further before adding the oil perhaps the warning light will go off by default. After that event, I began to notice intermittent low engine power, whereby I will match on the gas and the car would drag, then it might later pick after a long drag, it jacks into gear at times after a noisy rev. At whatever RPM while in motion, the car experiences difficulty to climb but runs smoother coming down a cliff.

I think it’s important to mention that the noise from under the hood is still there, and note; no Check Engine Light (the function works, came on when one of the spark plugs was removed for servicing).

When I went for computer diagnosis, code P0016 and P0017 came up which could be erased, but set back.

An oil change was performed yesterday to a synthetic 5W-30 oil, right fill, the filter was changed and the sump was opened to clean the oil pump mesh. The VVT Solenoid/sensor was cleaned off clogs, the air filter was observed and cleaned, the spark plugs too were cleaned, but with all that done, the rattling/tapping noise like of a chain, on the passenger side of the car from under the hood persists and the car does not pick up/accelerate correctly still, also there is a lot of noise (generally) maybe from transmission shifting delay or so, like the car is under an opposite directional drag. The most annoying thing is, there is still no check engine light.

I plan to service the transmission soon.

Additionally the car was earlier diagnosed to have exhaust Restrictions by one of my local mechanics and the catalytic converters housing were opened up and the content were emptied, the container was closed back up/welded and the exhaust reinstalled without catalytic converters, pending when I can afford a replacement. I still have doubts the catalytic converters were due for a change anyways. Their claims was that, back pressure was the cause for the low engine power which was my complaint from the start.