On a flat does it get stuck at 3-4k? and is it only in 4th?
How long have you been DD it/ has it sat?
Oil is not likely unless you are really using the wrong type of oil, something super thick. I'm assuming you put in 20-50w
When I got my friends car running he bought brand new injectors. Put them on and it ran fine for 2 weeks, then it started sucking hard core.
The gas tank literally had gel in it from gas that was more than 6 yrs old. We didn't think much of this because the PO said it was empty, so we had to put 5 gal in it anyway. The get somehow made it to the injectors, and they needed to be cleaned. The flow was horrible, like 110 per injector and one was actually clogged. Everything had to be redone in the fuel system.
I haven't followed all your posts so I can't really say.
Also doesn't sound like your other gears are going( yet) since its not "rocky" as you put it.