Shifting problems after changing carb gasket?

Hello,

I have a 351 W with an FMX in my car. The transmission was shifting fine until I put in a new fuel filter and carb gasket. Since then, the transmission is not shifting until much higher RPM (I don't have a tach so I cannot determine the RPM's). I have checked for vacuum leaks etc. and it appears to be fine. Any thoughts? Thanks.

Okay, I have verified the modulator connection. I will pull the carb off and re-install it, perhaps use another gasket. Thanks!