Recently bought a 05 with 49K original miles. I lowered it, wheels/tires, removed third cat and resonators, 250 amp alternator. Out of no where it started a hesitation under acceleration, its very inconsistent but once it starts its pretty much there for the duration of the trip. It does not seem to do it until the car warms up? and I can be doing 70-80, lay into it to downshift and accelerate and it wont downshift or go, just sounds like its on the rev limiter in limp mode. Since i found the issue I've replaced spark plugs (NGK) coils (Denso) EVAC solenoid, Mass air sensor (denso) car is showing no check engine light, idles fine, revs to the moon in park or neutral, no vacuum leaks so far, no smell from the exhaust, I disconnected everything from the stereo thinking it could be a voltage issue but no change, verified 14 volts, I had a scan tool on it while driving and it showed misfire cylinder 1&2 when it was acting up, but no change since plugs and coils, again still no check engine light, talked to a guy about a ECU and he said thats not a ECU issue, I'm thinking cam position sensor or maybe crank sensor? I'm literally stuck please help

 

you might try installing a fuel pressure gauge and see what pressure you are getting at idle, normal, and WOT

 

Outside of electronic issues.....
Three things to make an engine run. Fuel, Air and Spark.

Seems like you addressed the spark issue.
Air is a near gimme if everything is open and free of obstruction.

Fuel, though.
Anything from the fuel cap/EVAP all the way to the fuel injectors can affect it.
I've experienced misfires and loss of power due to a FAILING (not failed) fuel pump. The engine will rev fine, as it doesn't require a lot of fuel to rev the engine to a high RPM. At HIGH LOAD, the engine requires more fuel.... more power, more fuel. The engine will run fine at city speeds and light/average acceleration.... However, going up hills, maintaining interstate speeds, hauling something heavy (could just be 5 American-Sized adults with luggage) will require more fuel than driving unloaded at 55. Reading the fuel pressure at the fuel rail would be key here. I'm not sure if your car will have a PID readable on a scan tool that will show the fuel pressure. If the pressure is at or above the target for the system at lower load/rpm, and then falls off at high loads, then you then have to figure out if it is the fuel pump or fuel filter.

A bad fuel pump can still provide enough PRESSURE, but not be capable of supplying enough VOLUME. Pressure and Volume of fuel are what will be required to run at speed.