While you are at it, make sure your fuel pump is fully capable up top: here a drooping high RPM on the virtual dyno normally means that there may need to be more fuel delivery or pressure from the pump. The engine consumes much more fuel at higher RPM, and the pump has to keep pressure in that 40-60psi range. Again, if the fuel pump is unable to maintain this pressure the motor can start starving for fuel leading to loss of power, misfires or hesitation. Even a 10% drop can have you sucking air and starving for fuel, which is no fun on highway or under hard acceleration.
A failing fuel pump is one known trigger of this issue. The motor or gears within a pump wear out over time, eroding the ability of the pump to deliver fuel effectively. Most fuel pumps are designed to last about 100,000 miles, yet as they age their flow can fall off by up to 20%, a fact that is especially evident when the engine is working hard at high RPM.
Fuel flow can also be impeded by a clogged fuel filter, especially at higher speeds. As the filter clogs, the less fuel that can get through it and that forces the pump to work even more. The engine needs more fuel at higher RPM, and a restricted filter can cut fuel delivery by as much as 25%, causing hesitation or power loss. By replacing the fuel filter every 30,000 miles or so, it can prevent this and ensure the pump continues to work efficiently under any driving condition.
A weak fuel pump relay or corroded electrical connections are also a possible cause. Especially at high speeds, it may not be able to deliver the needed voltage to even one of the fuel pumps. A 10% voltage drop will cause the pump to gain almost 20 lb—is someone turning your gas into lead? The year before — 2017 — saw a recall for many of their vehicle models because the relays were defective and led to sporadic fuel delivery when at high speeds.
Fuel injectors can also help. When the injectors are clogged or failing, they will not be able to spray fuel properly and this could result in a lean condition at high RPM. A lean condition which decreases available power and can cause misfires or hesitation. Under full throttle a fuel injector that is flowing at only 80% has the potential to decrease engine efficiency quite drastically.
Fuel contamination is one possibility finally. Clogged fuel lines or injectors from dirty or water-contaminated fuel will slow the flow rate, causing the pump work harder to move fuel. Contamination of this kind can lower the efficiency of the fuel system from between 15% to 30% which is a huge deal breaker for high RPM performance.
For further information on diagnosis and repair of Fuel Pump problems, view Fuel Pump.