Joined: Jan 2011
Location: Olympic Peninsula
It sounds like you already got your answer now, but I figured I would add some reassurance. Every carbed car I have ever owned/worked on has idle drop with the air cleaner on. As already mentioned, final idle should be set with air cleaner and all vac lines installed. Just for giggles, I ran out and fired up a pickup with a 302, and watched RPMs at idle with and without the air cleaner. Seems to be 80-100 RPM fluctuation. If it matters, testing temperature was with the engine at operating temp around 180, and outside temp of 40 degrees.
1968 Mustang. 351w, T-5 Five Speed, 8.8, 3.73 trac lock rear end. Power, four wheel disc brakes, (CSRP up front, 8.8 discs out back) Shelby Drop...