Have you checked fuel pressure? I highly doubt it is because the 87 grade gas. It could be bad, dirty watery gas, but i have had 2 3.8l cars and a 3.1l car and always ran 87 grade because they don't need anything else and never had problems. Injector cleaner is good preventative maintence like blowngp said i usually do it every couple oil changes or just every so often to keep them clean at like 90 bucks a pop i don't want to replace them...