Having the proper Emulsion Tubes will enable you to get the best out of your Webers! Just tell us what size you need! Sometimes the Jets, Venturis and E-tubes are sized using a trial and error method. There's just too many variations between Porsche engines to state absolutely that a particular combination of Jets, E Tubes, Venturis, etc. will be perfect for your 911. Sometimes you will need try different jets, etc to see what will work the best.
F3s are not currently available!! We have plenty of F26, F7 & F24 E Tubes - these are the most common E Tubes recommended for the 911.