If the carb is the cause of your sluggishness you'll have to do more than spray cleaner down the throats--residue can restrict the jets and passageways, greatly affecting performance--it will have to be opened up and cleaned properly---and I've got to say--my previous advice to you lead me to get to a project I'd been putting off--cleaning my lawn mower carb--what a difference! The main (only) jet was nearly completely clogged. I've had three kinds of filters on various Weber set-ups--Rectangular with a chrome lid held on by clips distributed around the filter---the "oval" RamFlo type with the perforated chrome dome held on with a wire type spring clip---and a modified Triumph TR6 housing over a custom twin 30/30 Webers (two Renault 5 carbs) setup on a B20. They all worked ok--Does your sluggishness occur all the time--from warm up to running temp? around town and on the highway? Does your area use oxygenated gas? Is the distributor advance working? Check its operation with a timing light.