Interesting, mine sputters a bit at just above idle, and it falls on it's face at about 3500 RPM, maybe a little sonner. When free revving it to that it spits and sputters like crazy.
It could be your fuel pump, but consider this. Usually fuel pump problems show up at higher RPM's, not even out at higher RPM's because it's starving for fuel with a bad fuel pump. Could be fouled injectors, water in the gas, need a tuneup, timing could be off. If you have a Schucks nearby take it in and they will read any trouble codes free of charge. This should at least tell you where the problem is at if there is one. Otherwise it'll be some of the more traditional stuff.