I had a problem similar to this when I put the wrong warm up regulator on my car after a rebuild.

I don't know if you've had this problem before, or if it just developed, but if it just happened, I would consider taking the time to do some in depth diagnosis of the CIS fuel pressures per the manual.

Hopefully one of the guys who've spent more time with CIS can voice a more knowledgeable opinion on this.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...