SilvaPwr

hey i have a little problem, the spedo goes in and out on my car, and when the speedo works, i can gas it in 3rd, 4th, and 5th no problem....but now when the spedo does not work, when i gas it in 3rd it cuts out around 5k, and when i hit the gas it does nothing, almost like the ECU is cutting the fuel off...same in 4th and 5th but in different rpms and when i shift down or up it will come back in...i have put in fuel injector cleaner and doesnt help...what do yall think?