Shuddering problem sometimes during acceleration

So first off the car is in excellent shape, you can clearly tell that besides the normal maintenance over the years that there has been no other wrenching anywhere on the car, at least not anywhere the eye can see. I have had it around two weeks the previous owner had just gotten a tune up during which plugs were changed due to car displaying misfire codes, after being changed car no longer misfires but it still has the stutter while accelerating from a stop or lower speeds it normally happens around thirty to forty five mph; what it does it when reaching 1,500 to 1,600 rpm's they will bounce up to 2,000 to 2,100 rpm's then back down. It will do that a few times if I do press gas down further to power through it or let off for a quick second then re-apply the gas, the rpm's will then rise and shift through the gears perfectly. Thinking it was injector issue I added a Chevron fuel system cleaner and it helped the issue by the rpm's no longer bouncing, but reaching the spot they once began bouncing and instead would almost surge through as if the injector was clogged but still managing to get squirts out. Then after "surging" their way up enough to shift or I give the car more gas to power through it, or releasing and re-applying the gas. However, the rpm's get there they reach the shift point, shift and then run through rest of gears just fine. This only happens sometimes, and it is always during acceleration never decelerating that it takes place. The only lights/codes the car is showing is for the rear brake pad wear sensor because the shop that checked the brakes broke it sometime while they were inspecting the pads. Because I still have around 60% to 70% left on them according to shop. I am planning on taking a video/videos of the issue because what it is doing as well as the way the car feels while issue happens is very hard to explain. If anyone has any ideas I am all ears.