to me i think after i started using 87octane gas my car feels weak...started to bog and lag around 4200rpm then lags till 4700rpm then backfires this only happen in first gear after that its all good... weird! and today checked my spark plugs 3 are still good but the upper left one facing it from the driver fender is all burnt up...

 

Maybe your using cheap gas and your injectors are starting to crap out? Your not using Arco right?

 

no ARCO only chevron and in desparate times 76