As your Rodeo is a 95, it is speed density, not mass air. What that means to you is that your truck will not be as "friendly" to mods that introduce more air, or allow more air to exit the engine. There is some variable programmed into the ECM, mostly controlled by the MAP sensor, but not much. In MY EXPERIENCE, I have noticed that when "playing" with speed density, they can sometimes run a little to lean, and possibly overcompenstae, and run too rich. This does not happen with every make and model mind you, but its something to watch out for. On you next fill, try going one octane rating higher, and see if it stops the "ringing", and if not, go one more. If that doesnt help, remove the Air filer, and replace it with stcok one. Now if you stop the noise with the fuel canhge, you are experiancing "ping", and it is natural in some motors, as increasing airflow, can cause a slight amount of detonation. The higher octane wont help performance in any noticable way, but if it stops the ping who cares. If its not that and it stops when you place the stock fitler assy back, I recommend calling Jet Perfomance, and they can recal your ECM to compenstae for the canges..including the tranny(if its electric)..

My 2 cents..

Chase