I'm wondering if anyone can point me in the right direction with this?
My battery died one day, and while I was driving, I had a weird bucking/jerking while cruising. I replaced the battery, and the issue is still there.
It's the most noticeable in 3rd-5th gear, while at part throttle. At 70mph just cruising, you can feel it jerking. The RPMs never drop, and there is never a miss, so I don't think that it's a fuel or ignition issue. I did pull the plugs and they all look good. I also cleaned the MAF, and made sure that the battery terminals are clean.
When it happens, it's always under vacuum, and my boost/vacuum gauge will increase vacuum also.
I used Evoscan to monitor the throttle sweep, thinking the TPS was going bad, but the throttle sweep looks amazing.

Any ideas on what it could be?

 

Do you still have the stock coils? Had same symptom, upgraded the coils & no longer had the part throttle bucking.

 

I do have them, I think I will try that, thank you!

 

I swapped in the stock coil packs, same issue. The thing I've noticed is that right before I hit zero vacuum, it starts to have the issue. I'm thinking that there is a vacuum/boost leak somewhere.

 

THE ISSUE HAS BEEN FIXED!!
I have a Walbro fuel pump installed, I needed to remove the factory fuel pump resistor so that the pump would run at 12 volts all the time.
No more bucking and jerking!