Question regarding Block Learn Map (Fuel Trim)

Hello guys,
Let me just say, I've stumbled across ScannerDanner's YouTube channel, and it's been an eye-opening experience, watching the videos. However, I have this very specific issue with my car, and I lack the experience and can't seem to make logic of what seems to be the problem on my car.
The car is a GM based - Opel Calibra, with a 2 liter 16 valve DOHC petrol engine. The problem with the car is that, it lacks power throughout the whole RPM band, but it's especially bad at low rpm and/or when pulling away from a dead stop. The good news is that I have parameters from a proven working car with the same engine, so please keep reading carefully.
So, the first issue that I'm seeing is the MAF sensor signal value. It reads 0.34v (5.51kg/h {1.53g/s}) on idle, even though it's supposed to read 0.7v (12 kg/h {3.33g/s}). Again, I've tested/witnessed this myself on a proven working car, and the Autodata software confirms these parameters. I've also probed the sensor directly with a multimeter and confirmed the values, so I know it's not an ECU fault (it's an analog sensor by the way). And, the MAF sensor itself is NOT the problem, since I've swapped sensors with the proven working car, and each car got the same results it did in the first place.
What's blowing my mind is that, although the MAF sensor is reading less air than it's supposed to and the mixture is supposed to be LEAN, the EXHAUST reeks of unburnt gasoline, meaning the mixture is overly rich for some unknown reason.
Also, the engine producing a lot of vibrations, and the vibrations increase as the RPM increases.
The only time the engine is performing acceptably, is when I'm cruising on the highway (even in 5th gear) at a constant speed for a while, and then press on the accelerator.
Now, pay attention at the scantool data, because I want to pinpoint another weird thing, and that is the fuel trim values (BLM Idle and BLM Partial Load). BLM is basically another name for long term fuel trim. As a reference, the neutral (0) point for these values is 128. Anything above that means the engine is adding fuel, anything below, the ECU is subtracting fuel (from the default values). So, looking at the picture, you can see that on idle the ECU is adding ~(128+6%=136) of fuel. And the fuel trim when the engine is at partial load is 111, meaning the ECU is asking for -13.3% fuel. And this is also visible when looking at the injector pulse. On idle, the injectors pulse is at 2.2ms. When partially loaded (15% throttle), the injectors pulse is even lower, at 1.18ms. (check the second picture for partial load data).



Lastly, please watch this video and check out the horrible throttle response and slight misfire.


Here's a list of things I've done and ruled out as the problem.
- Tested Cylinder compression/pressure (14 bar/ 200 psi each)
- Tested Fuel pressure (3.5 bar/50 psi)
- Checked Timing belt alignment - it's perfect
- Changed Spark plugs, HT leads, Coil pack
- Cleaned throttle body, Smoke tested the intake and vacuum pipes.
- Straight piped the exhaust just to test if there's blockage somewhere - there isn't.

And yeah, almost forgot, there's a bit of white smoke coming out of the exhaust.

The car is fully warmed up on the picture, although the outside temp was about 5 Celsius/ 41 Fahrenheit.

Have you checked for head gasket failure?