Good morning Scotty. I have a 05 Cadillac srx v6 130,000 miles. The check engine light started flashing and a diagnostic check revealed multiple cylinder misfires. 5 of the 6 were misfiring and it was difficult to get beyond 40mph. Since the truck was as old as it is I replaced all of the ignition coils and the spark plugs. Now im getting a p201 and a p301 error code "cylinder 1 misfire", "circuit open". The check engine light still flashes when I excelerate and my gas milage has gone down from 18 to 14 mpg. but at least I can get it above 40 mph. I disassembled it again and checked all the coils and spark plugs, but still the same issue with cylinder 1. What else could I do?

do a wet and dry compression test of the engine, odds are #1 cylinder is worn out inside

Thanks Scotty. If the cylinder is worn out can it be reasonably fixed?