Sputtering '92 325i

["Douglas M. Max" <DMax@xxxxxxxxx>]

Hope you can help me save some money and get my car going well again.

A '92 325i with 115K.  Starting off after it's been sitting, it does
great for quite a while.  Sometime after it warms up, I'll get
sputtering whenever it's below around 3,000rpms.
At slow speeds, it makes a backfire like noise, but don't know enough to
know if it's a real backfire or not.

The exhaust has been getting throatier, and someone told me that a pin
hole might be causing this...though I had the beginnings of the symptoms
when I passed inspection a year ago, so makes me think not that, or not
just that.

Coils have been suggested.  Can a handy DIYer replace coils? I've got
the Bentley, but thought I'd ask.  I've been suggested that it might be
the wires going to the coils (but someone said my car doesn't have
ignition wires).

Lots of advice, but nothing authoritative.  I also thought maybe fuel
pump (gotta go sooner or later).

Me, I really don't want to just have some mech replace everything hoping
he/she gets it right.

Final question:  will a dealer run a diagnostic on it, knowing that I'd
take it elsewhere to get fixed--can I ask them to do this for a fee and
would it likely uncover the particulars of this problem?

Thanks a bunch whatever you can suggest.

Doug in NJ
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