Thanks guys you have been a lot of help! P.E.Haiges the reason I'm changeing then is I can hear a strange sound comeing from injector number 4. I guess it would be called "nailing" the car also skips when started. Since the glowplugs are probably original, as are the injectors I think there due for replacement. I want this car to run 100%.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200