Hi guys, so basically, i've been having a colossal amount of issues with one of my cars. The car in question is a 98 Mustang, it has the 3.8l in it. I've been wasting alot of money on it, just trying to solve ONE issue, then i discover more issues, and it really just has been a nightmare. The issue in question is basically it'll start jerking really hard when i try to accelerate, kinda seems like its trying to stall or something; but only if i get on the gas pedal moderate to hard. And The RPMS will barely climb and then stop climbing for a brief second when it jerks back. It is a manual and it shifts fine. But it'll rev fine in neutral and the RPMs will climb like normal while in neutral.

It only threw up 3 codes when i plugged an OBD scanner in it. 2 for 02 sensors (i removed the cats and the 02 sensors) and one code for the EGR valve, i replaced the EGR solenoid but that didn't do anything; but i don't think a faulty EGR valve is to blame for this issue.

After changing the solenoid, i reran most of the vacuum lines because none of them were sealed properly, so i fixed all the vacuum leaks, i replaced the coil pack, i replaced the spark plugs and spark plug wires, i made sure all the cylinders were firing properly, checked the firing order, did a full engine flush, changed the fuel filter, oil filter and now im just gonna check the fuel pressure and i guess work from there.

Any suggestions would really be appreciated, i've consulted so many different forums so i figured why not see if anyone in my favorite forum can give me an idea. Thanks in advance.