I just changed the fuel injectors in my 1997 Malibu 3.1. There was no adjustment for the lifters. The rockers are torqued and if you still have noise you must replace the pushrod or the lifter. My problem turned out to be a noisy fuel injector. A 2000 3.1 I worked on after I did mine also had noise but the injectors were not the source. That one had a bad(very slightly bent)pushrod but ran fine with no repair.