Alexandre,

For what it is worth (I am not an expert):

I believe your Racor filter should be 10 micron and your engine filter should be 2 micron. I believe you will get too much vacuum when double-up and place 2 micron in both locations.

Also, think about the logic: Assuming that you source quality filters, particles larger than 2 micron are going to get stopped by the first 2 micron filter. In that case the second 2 micron filter is only increasing the vacuum pressure on the engine's fuel pump.

I am always leary of advice that goes something like this: "X is good so 2X is better." I had a knowledgeable boat engineering company ruin our watermaker by using 4 times the required amount of chemical to pickle the watermaker. When I asked him about this he said he thought if a little was good, more would be great.

I hope this helps...if not it gives you another view.

Best,

Bill
BeBe, SM2k, #387