I did the same as well. During my REV400 upgrade with the S/C off I noticed how dingy that carpet was (it was filthy). Cutt it all out, cleaned the firewall, and applied DEI Reflect-a-Gold 12x24 sheets. It was a complete pain in the ass, mainly just really time-consuming, to do even with the SC off.
2006 Lotus Exige: Avery Matte Graphite wrap, partial built motor (9:1 Mahle pistons, Ferrea Competition valves, ACT Clutch, ARP head studs), REV400, Nitron SAs, BOE QS exhaust, Ultradisc rotors, Moroso Oil pan, Circuitworks oil pump, CF Stuff (Cup Roof, ReVerie diffusor, side scoops, APR air dam, craftsquare mirrors), Worksbell quick release, Odyssey PC625, Morimoto Xenon HID, BOE Rear Oil Cooler, Difflow Aeroplates, BOE Swirl Pot, DaviesCraig EWP, Reversed Heater Matrix