I want to know about the upgraded PW6000 Avianca A318s. Why did those get upgraded? Did they not produce enough thrust already?
The PW6000 was a second option for engines on the A318, not an upgrade. The rest of the A320 series at the time had options of CFM or IAE engines. The thrust was comparable to the CFM option, but the initial design had worse fuel efficiency than expected, leading some customers to switch their orders to CFM. In the end, only LAN bought A318s with the PW6000 engines, taking delivery of 15. These were later sold to Avianca Brasil, who no longer flies them.