Need help and tips from barista here ! Today i just tried pulling two shots using 14.a5g of coffee with 5s preinfusion 5 s ramp up to 9 bar for both. First shot pulled with grind size slightly coarse than slight choking grind. But its was very sour with bitter aftertaste and sour after taste with subsequent sip. The second shot with grind size slight choking till initial extraction was oil followed by crema. The taste was less sour but sour still with mild bitterness. First shot yield 25g within 35s and the second shot yield 22.2g within 44s.
Im using portaspresso pg and oe pharos 2015. The pg was also preheated multiple time with water just off boil.

Sounds like your grind is too fine and the shots are running too long.

Sometimes sour and bitter are a challenge to distinguish. I usually find sour to be an immediate flavor. When egregious bitter can also be immediate. But more often than not, sour fades quickly while bitter lasts as a prolonged aftertaste. Your parameters seem over extracted and likely bitter to me. Coarsen the grind and get them flowing faster. See if the bitter disappears.