Ok I'm going about 80 on the freeway (open throttle) then when I slow down I started hearing this pinging noise when I accelerate. When I accelerate, noise starts at 1500 RPM. I think its coming from intake manifold, some where or by the injectors. My friend mentioned that could be it valves. My plan is to clean intake manifold through throttle body with seafoam and adjust valves. Anybody had simmilar problem?