Within the last three weeks, My 98 chevy ext-cab Z-71 with 33,500 miles has lost power and is now pinging under load. I changed the fuel filter to no avail. Checked spark plugs but they were still good. I checked for vacumn leaks but couldn't find any. I checked fuel pressure and at idle it reads 54psi. I reved it up real quick and it goes to 62 psi, than drops back to 54psi. When you partially turn key to activate fuel pump it goes up to 61 psi and than drops down. Factory helm service manual says fuel pressure should be 60-66 psi with pump on and motor off. Says it should jump up to about 66psi when you rev the motor real quick. Mine only goes to 62psi. Could I have a fuel pump problem? My pump has also gotton alot quieter than it used to be. Can anyone tell me what elso I should look at to fix this problem? I do not get a SES light and no codes are stored on the computer. No misfires or anything. Truck feels like it has a restriction. You give it gas but it hardly picks up any speed. Gas milage has also suffered. Thanks for any ideas.