i have a s4 NA
car runs like **** under 4k rpm, but after 4k the car pulls hard to redline(secondaries kicking in?)
car has no power under 4k, bogs down and sputters/shakes hard at idle
its hard to roll off in 1st gear unless you give it alot of gas.
compression is good

so far iv replaced the spark plugs, old plugs were crusty and looked like ****.
imma try to look for a new fuel filter or fuel pump tommorow

any ideas?

 

I bet its the primary injectors are dirty or has a bent needle. try swapping primary and secondary injectors see if the problem changes. If there is no change they may still be fubar but its an eazy free place to start.

 

I second the dirty injector theory. It could also be a failed or failing primary injector. If you are going to go thru the work to pull them out, I would recommend sending them out for a professional cleaning/test. Its not that expensive, and should be done every 30k miles anyway...unless you know yours have been done since then.

It could also be something as simple as a connector fallen off a primary injector, or a broken wire in the harness to the primary injector. I recently had my injectors done, and found multiple wiring and connector issues in the area under the intake manifold. I fixed the wiring and put in new connectors.

 

cool i should get mine done soon too