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Q:

had replaced all coils,ignition mudule,and plugs and still have mutiple misfire. on 1999 Pontiac Grand Am

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
replaced parts and still the same no power and rough idle
(2) Answers
Any other codes besides misfires ? Any ability to read live data? Access to a vacuum guage--easy check for valve related problems often overlooked is with an old-fashioned mechanical vacuum gauge.
Sounds fuel or compression related. Have you checked compression or performed an injector drop test?