As far as sand filters? No loss of speed as far as I know. 1-2 mph or so I think. the 190 air intake is behind the engine cylinders. The bulge left and right over the cowling is a housing to accomodate the air intake pipe snaking around the cylinder heads to get the feed to the supercharger behind them. On the sand filters that I've seen, they are placed where this bulge is on the cowling and take in air externally, filter the sand there, then duct it inside.
Similar to the diagram here, on the upper middle right side:
On the similarly-shaped high-alt ram-air compression supercharger intake used on later models this only slowed the plane down a barely noticable amount.
In short: Fw190s were impacted less than Bf109s were, which weren't impacted all that much to begin with.
[edit: grammar fix]