Cranks but does not start, sometimes starts but then shuts off

Hi folks, My name is Keith and I am new to the forum. Please help me with the below:

I have the vehicle listed above comfortline, and for about three weeks my EPC light came on and went off and in that same time I would lose throttle completely even while driving on the freeway at high speeds. It would feel as if I lifted my foot from the gas but I did not. I will then simply lift my foot and drop it again then it goes fine. Last week when EPC light did not go off and I lost throttle completely. Towed the car home because it would not accelerate of course. I then tried to start when I got home and would not start, just swing and swing but would not take, Left it and tried the next day, it then started and idled erratically then switched off. During this time still no throttle.

I have tested my accelerator pedal in a Polo Vivo and it works but the Vivo one also did not work in mine. I have put on a different throttle body (also from a Vivo) and it does the exact same that mine does. Car just idles for about ten to fifteen seconds then switches off (as if timing was off). But timing was never an issue before the throttle issue, then the starting/idling issue.

Plugged it onto VCDS and it picks up - Accelerator pedal position sensor 1/2 (P1639).

on a second diagnostic it speaks about map sensor (manifold absolute pressure). Also mentions something to do with injectors, now I do not know if this is the case because of a faulty map sensor.

Please shed some light as to where to start first without spending too much unnecessary money. I have already spent about R1500 in diagnosis and still cannot be pinpointed to the problem.