I'm at a loss

[coldweatherftw]

So, I have a 1986 325. The issue I've been having is that the car wants to sputter and choke, attempting to shudder and die upon acceleration until it hits about 2500 to 3000 rpms, at which point it catches power but I can still feel it not running at full capacity. It also tries to idle around 500 rpms and wants to die just while sitting. I've replaced the fuel pump relay after reading a few other threads, but the problem persists. Any ideas?

[02Pilot]

First thing I'd look for is a vacuum leak. Lots of old rubber plumbing in there. A smoke test will be the most efficient way of doing this, but the M20 is not as packed in there as more modern motors, so you may be able to find it without.

Failing that, test fuel flow and pressure per Bentley (you do have a Bentley manual, right?). I can't recall if the M20 has a cold start injector like the early M30s did; if it does, pull it out and see if it's leaking.

There are other possibilities, but let's eliminate the basics first.