Boeing has developed a number of performance enhancements to the Next-Generation 737 that reduce fuel consumption and emissions. Elements of the PIP have been introduced gradually on the 737 since early 2011.Boeing has delivered more than 490 Next-Generation 737s with a PIP.oeing has developed a number of performance enhancements to the Next-Generation 737 that reduce fuel consumption and emissions. Elements of the PIP have been introduced gradually on the 737 since early 2011.