Could this exhaust conversion/removal of air pump have anything to do with this condition.

I own a 1978 porsche 911sc and recently did some upgrades. I replaced the stock exhaust system with a SSI pre-75 exhangers and danske stainless muffler single outlet sound great. The technician removed the air pump/smog pump assembly and capped off openning at block. Car runs great but I noticed the RPM's seemed to drop across the board. Cold start process rpm seems lower and after driving/coming to a stop rpm is 600-700 or so. It's not until engine meets proper operating temperature that the idle comes up to where is should be 800-900 for so. Once warmed up properly idle seems good. Could this exhaust conversion/removal of air pump have anything to do with this condition. Thanks for any feedback.

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: Personal Touches - 911 (1965-89) - 930 Turbo (1975-89)

[Nick at Pelican Parts]

Depending on the exhaust design you could have different back pressure changing your rpm limit a more restricted exhaust will give better mid-range power but lower top end. A more open exhaust will give more top end power but mid-range torque will suffer. This should not have much of an effect on your idle speed

- Nick