I had someone ask me if I was any faster because of my new rig.
There are two things that actually did make a difference. Everything else improves immersion but hasn't had any impact on performance. Granted I started out with good controls.
#1 The most important thing was having a rigid chassis to mount my controls. There is nothing more frustrating than braking hard and having your pedals move or having other controls move. On top of that my original rig would absorb a lot of FFB and make everything feel less crisp. So the Sim-Lab P1 was absolutely the biggest improvement. It also allowed much better placement of controls.
#2 The HE pedals made a big difference as well and required a solid chassis. Being able to adjust the angle, travel, and pressure needed for all 3 pedals helped a lot. I found the CS 3.0 with strong springs installed was just too effortless on the throttle and clutch. It was hard to modulate the throttle when the peddle felt like it just dropped to the floor and I had to actually hold l my foot back. Of course brake modulation is the big deal that really matters as you go around a track. Over time I've adjusted all of the pedals and they really do make a difference.
Everything else has helped immersion but hasn't made me one bit faster.
Some upgrades were trickle down from other upgrades. As an example, after setting my brake pedal to higher pressures, I would get a sore back with my used car seat which otherwise had worked wonderfully. So I got a racing shell which fits me like a glove and gives me the back support I wanted. No sore back after extended sessions
For immersion I still believe that motion and tactile complete the experience in VR and direct drive systems are way way way over hyped. I like my SC 2 Pro and have it configured well. I love my new PSE GT3 wheel and Momo Rally wheel, but they don't make me faster.
Once I have my new flight controls in place, I intend to put a pin in my rig and will call it done. One day I'll consider a full motion setup, but currently they are too bulky for my requirements and I still think they are evolving quite a bit. I love the new NLR traction loss system and I think other motion systems look great, but I think that more fully integrated solutions will evolve.