PVA stands for Packet Velocity ASIC, a hardware acceleration chip in F5 BIG-IP that provides:
• High Performance L4 throughput
• Denial of Service Portection
• Load Balancing

PVA was introduced to speed up packet transfer rate by introducing ASICs to fast-switch packets. This works by the tmm process checking an incoming syn packet against a flow, if it matches then it pushes a rule down to the hardware ASIC to fast-switch this flow. That can cause issues with tcpdump - only the first packet is seen. This was made obsolete as it became faster to implement this in software rather than hardware (which had introduced issues with upgrading the firmware). However, ePVA is a much smarter way of selectively speeding up certain packets, done in software. I don't have any more details about HOW it does it though. I think PVA is ASIC, but ePVA is FPGA.

And on the performance (layer4), there is the availability to the use the Fast HTTP profile, which is associated with PVA.