F1technical.net

Renault was the first team to add a “hump” on top of the engine cover . That was a necessity because of the new 2004 rules of FIA about the minimum size of the engine cover for sponsor needs . Renault instead kept the height of the rear part of the engine cover relative low and placed an extra fin “hump” on top of the engine cover to fulfill the new rules . The low rear part offered a better airflow to the rear wing . Since then almost all teams gradually adopted a similar design (Ferrari , Mc Laren , Red Bull , Toyota )

I think it was the year the turning vanes got developped. The F2003 GA had some sort of junction between barge board and side pod as seen on this pic, but the extention of the floor in front of the side pods appeared in 2004.
I remember Williams or Honda came up with that at one italian GP (imola or monza). I'll try to find a pic.

already explained here viewtopic.php?f=6&t=5153

The FW26 features a distinctively short nose cone, with the the front wing main plane and associated assemblies mounted on extended 'tusks' The startling interpretation of the front profile has been conceived in tandem with a twin keel monocoque design, aiding air flow both under and over the front geometries of the car, and improving global aerodynamics right through to the rear wing of the FW26. The car's behaviour now relies very much on the efficiency of the front under the nose, more than ever!
The efficient implementation of a twin keel design aids air to flow under the car smoothly, and allows a less turbulent airflow into the sidepods

The design was abandoned since then .............