Diagnose this problem Please., Studdering sorta. Options

[x_itchy_b_x]

Well this problem has always been there since i bought the car back in stock form.
Alright while holding the gas in like half way in 2nd or 3rd. at around 3k rpm. i just hold the rpms there and the car front of the car will raise and lower. and accelerate and decelerate in a pulsing way. like RRRRR rrrr RRRRRRR rrrr RRRRR rrrrr. lol im gunna say since im using stock ignition, IE coil and wires with larger injectors running more fuel maybe it needs more spark to ignite the gas better? then i was thinking. it also did this in stock form that that wont really explain why.
maybe poor contacts on one of the distro pins? or maybe iunno. can anyone give me there input.
Its not hindering performance cause once you give it more gas rather than holding it at a certain rpm it takes off and goes away?

[946thGenGT]

Probably not a big help, but back when I was driving my 4th Gen I had a similar problem. I couldn't go past about 50% throttle without having the same symptoms you described. Did plug wires, didn't help. So then I did rotor, dist cap and plugs all at once (maybe I should have done one at a time to find the source of the problem but oh well I was due for a tune up anyways) and all was well. One of my plugs was really corroded so I suspected it to be the culprit.