I have a 87 gmc Serria truck with 43,000 miles with a 5.7 fuel injection system. This truck sits most of the time in my shop, only used to deliver materials to a job site. For the past year, this truck has driven me crazy with its running habits. It starts easily cold, but after it warms up, the only way it will start is to pore gas in the top of the intake or spray starter fluid in it or wait until it cools down. I have replaced the fuel filters, injectors, fuel pump relay, pickup coil, and fuel pump. Please advise me of anything else I should be checking.