The 40LA HAS a boost port as do all the LA series and it is rated at the same HP by OS as the FP. 1 HP@15,000 rpm. The big difference in the two series was the heads. One has a four bolt head and the other a 6. Oh, and the LA is blue (well some are) but I don't think that affects the power output. Cost effectiveness is why they changed. Power and reliability remained about the same.

It's the same reason OS went to the SF series from the FSR. It was less costly to manufacture a one piece Crankcase than the two piece case the FSR's used. One less casting to make and several machining steps less. That was one reason the 50FSR and the 108FSR lasted as long as they did. They had one piece cases.