Engine lacks power on 1995 Chevrolet Camaro

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Engine runs rough at idle and lacks power throughout RPM range. I have changed the IAC valve and replaced the plugs and wires. I have also checked the EGR valve and it seems to be working and is not clogged. This has been an intermittent problem and the cars seems to run normal sometimes for a couple of days in a row the odd thing is that driving in the rain seem to cause the problem but it does not go away for several days maybe weeks after the wet conditions has gone away. This car has a OBDII plug with a OBDI system and I am having a hard time finding diagnostic equipment locally. The SES light comes on intermittenly but not always when the engine lacks performance.
(1) Answer
You can use a genysis scanner for the OBD-I car with an OBD-II plug. How is your gas cap. I know this sounds really basic but is water leaking in to your fuel when it rains. This will cause a Check Engine Light ( usually a lean code )and the car will run rough for days after water gets in the fuel. it could be a wiring/sensor issue that is getting wet, but usually the car just dies. How is your air cleaner? Is it getting wet?