Low power under 3k rpm

My 1988 Pioneer (4.0 engine) feels like slow under 3000 rpm; when I hit this "breakpoint", it feels as if a turbocharger switches in (maybe not that extreme but it feels much stronger).

I'm about to change the distributor rotor, distributor cap, spark plug wires and spark plugs; this should help a bit as I think it might be due to misfires, and I want to get a better gas mileage as I think 15mpg is quite mediocre for this Cherokee with 30 tires. Now, is there any other thing that could be causing this low power under 3000rpm?

Regards

Distributor indexing? TPS?

I don't think it's the TPS as it would fail at any rpm, it's just clearly just at 3krpm when it starts being stronger, so I think it's an ignition issue. I'll check the indexing, although I think changing the rotor, cap, wires and spark plugs should make things easier. I just want to know if anyone has had this kind of experience so I can be 100% sure I'm exchanging the right parts.

Is it 3k in any gear? If it was starting to crap out when you hit 3k I would say it was the coil, but yours is the opposite.

You could have a CPS that is weak until the pulses start coming at a faster rate.

I could say it can be felt at 1st and 2nd gear; at 3d and 4th gear it's not noticeable and at 5th I would have to drive about 150mph to get the 3krpm with my crappy 3.07 gears (soon 4.10).

So, the parts I listed are relatively "cheap" to buy, but the CPS is rather expensive, so I would really like to be 100% sure; I had also thought about the CPS, but I have no idea on how to diagnose a possible failure on it, and, can it be cleaned?

Regards

If it is truly rpm specific, how would the engine know if it is 2nd or 3rd gear?

If you put the accellerator to the floor, the power comes up when you hit 3k, right?

Have you had the distributor out for any reason?

It's 100% rpm related, it's not noticeable at higher gears but I'm sure it still happens. I haven't tried it in neutral, not sure if it could be noticed because it revs up quite quickly.

I haven't touched the distributor, the only thing I did was change the spark plug wires and spark plugs about two years ago, the old ones were crappy; since then I haven't replaced spark plugs nor wires nor anytingh related to ignition; that's why I want to replace rotor, cap, wires and plugs. Do you thing this could help? And, could it be timing-related?

Regards

I just bought new rotor, distributor cap, cables and spark plugs; I had only time to replace the rotor and distributor cap, since it was dark, I didn't want to mess up with the order of the cables. I also changed some of the vacuum lines as they were coming off all the time from wear.

The XJ now feels much more responsive; I was amazed on how worn-out the distributor cap and rotor looked; I'm sure they hadn't been changed in many years (at least I hadn't changed them since I own the vehicle). As soon as I'm home early I'll change the plugs and cables to see if it improves even more.

Now, I still feel more power over 3krpm, but now I feel power increases gradually, and since the 4.0 engine has it's hp and torque maximums around 4krpm, I now believe it's rather normal.

Regards