1995 GMC GMC User Comment / Complaint

We own a 1995 gmc diesel 4x4 truck. we had an extended warranty to 100,000 miles. our truck was in the shop at 127,000 miles to have the 4th fuel injector pump replaced. gmc had added a 25,000 mile extra coverage on this part above the extended warranty. i feel they recognize that they have problems with this part. i have contacted customer service--no help. i have contacted the exec offices of gmc--no help. i contacted the bbb of autos who had human resources of gmc call me--no help. i am having a hard time understanding that no one seems to think that 4 replacements on a fuel injector is excessive. am i spinning my wheels?--pardon the pun! i have data to support these claims of service. they were all done by gm dealers and gmc has a record of repairs. reference # 1-74841039. i felt that gm should replace the part for free-- even if i have to pay labor. is there a way to find out the history of this part and if it has had as much trouble for other owners of diesel fuel injectors.