Assuming that you live in the UK, or a developed country, you seem to want a lot of grief in exchange for a small gain in power which you will seldom use! A comparative small power increase could probably be more easily gained by a good remap.
Removing both catalytic converters and replacing them with straight pipes and Lambda probes is not straightforward, or guaranteed to make an improvement, and it would be a reason for failure of an MoT or equivalent (TuV, Controle Technique etc) in any civilised country.
This sounds like a victory for enthusiasm over improvement, and would be best left until you can use maximum power for more than a few seconds at a time . . .