I have a 1991 Accord SE with 180,000 miles on it- during the summer it began running very rough, starting spuratically (usually only when the car was cool-- early morning or night) and the gas mileage dropped to around 19 MPG from ~26. We had the distributer, wires and plugs replaced. The EGR valve was also checked, and the EGR ports were bored. It ran better with fewer episodes of engine power loss, but the gas mileage remained unchanged, and the starting problem worsened as the summer went on. Since winter has hit I have not had one problem with the car not starting, but the gas mileage seems very unpredicatable (never getting above 19 but at times as low as 15). Any help would be appreciated as I have already put $900 into it with little return.

 

Based on everything you've done I'd have to say your injectors are likely causing this.

 

Pull the vacum line off the FPR on the end of the fuel rail and if it has raw gas in it the diaphram is ruptured.
Not starting in hot weather is a common complaint of a Main Relay with cracked solder joints