I talked to a friend of mine that just got his car tuned and he told me he dropped in hp because he tossed his fmu and got bigger injectors. He dynoed his car at 521rwhp before with his fmu and now only 509rwhp with upgraded inj. The tuner told him it's the way the injectors are spraying. Even though the afr's are the same, there is something about spraying fuel at higher pressures that makes more power. It's something that he has not learned about yet but is true. He was saying there has been many times were someone he tuned has came in with dropping fuel pressures up top but compensated the afr by adj the fuel maps. Then next time they come in with an upgraded pump it would add like 20+hp. He also said even though the fmu will create more power it is more dangerous and can lean more to detionation.

Anyone ever hear of this or can explain?

 

While it might be true I wouldn't trust my fuel system to higher fuel pressures (FMU) and risk locking injectors. Now... I wouldn't trust the FMU either.. FMUs are known to break engines for their unreliability... lean engine=detonation=lost $