boost92Si, are you running 8.5-10lbs of boost on stock injectors, a 12:1 FMU, and an intank pump? How is your intank pump able to put out enough pressure to support the FMU? Most of the "high-flow" intanks can only generate about 60-80psi MAX. Like I said above, they can flow high volumes, but cannot generate high pressures. Even if you set your static FP on the low side, let's say about 34psi, at 8.5lbs of boost, a 12:1 FMU is going to raise fuel pressure to 136psi(8.5 x 12 + 34), and I doubt your intank is going to be able to put out that much pressure. True, a decent intank pump, or even the stock intank pump is enough for any "near-stock" D16, but when you're dealing with an FMU, high pressure is needed, and intank pumps simply cannot generate enough pressure for an FMU setup(unless you're running low boost, like the GReddy kit in stock trim). Since an FMU relies heavily on fuel pressure, when you turn up the boost, you need more pressure. This is when an inline pump comes in. If you're running the GReddy kit in stock trim at 4.5lbs of boost, the pressure increase under boost with an FMU pretty much maxes out an intank pump(pressure-wise, not volume-wise). The GReddy box probably accounts for this by adding more duty cycle to the injectors to keep you from leaning out at that boost level, but it was only designed to work at 4.5lbs of boost. As I've cited before, DRAG and REVhard kits whose boost levels are between 7-9lbs include inline pumps to supply the 12:1 FMUs that come with them.

Sorry, I kinda rambled on there...
If you are not running a 12:1 FMU setup with just an intank pump, please disregard this post.