Alfa Romeo Repair: alfa 156 ts poor starting, throttle position sensor, sensor tps

Question
I have alfa 156 ts the car was cutting out everytime i stopped at lights ect. then the other day it would not start it was trying then it did sort of start after alot of turning and trying only it did not take any throttle you had to hold it just above idel or it would just cut out it was also doing a lot of back firing ect.
have a garage i go to and thay have a reflex 3130 when thay plugged it into my car it came up with somtning to do with the throtel thing i dont understand anyway would this cause all thes thing to happen to my car?. I had it into arnold clark alfa in edinburgh and thay put a nev 02 sensor on but it has not made any diffrence now i have this problem of not starting an you help CC

Answer
These are the classic symptoms of a bad throttle position sensor (TPS) or a bad connection to the TPS.

The first people were on the right track.  The second outfit was just guessing.

By now you probably also have fouled spark plugs. Please use NGK plugs if possible.