saftey mode??

[hugoz240]

i just bought a 240sx with a single slammer engine and there seems to be a problem...in 3 ,4 and 5th gears it wont go over 3400 rpms my friend was telling me that the car is in a :safe mode" becuse of the maf senor is cloged or the air to fuel ratio is messed up...all i no is that it sucks and i want it fixed so can anyone please help me find out what the problem is???? thanks