You reckon your car would lap faster than a sorted CSL? Genuine question, same driver, same track. I honestly can't see it, but then I haven't driven yours or a CSL around the Ring at 10/10ths.
There's also the point that you've a £40k+ car worth £18k and going down, where as that would be a £25k CSL and still worth £25k in a few years time when you're bored, because of its rarity... it might be more on consumables, but it's a darn site less in depreciation and dead money. Likewise a 'lost all its money already' Porsche.
Why does it have to be the fastest thing on the track?
Not trying to rain on your parade here, but when we're talking the level in performance and money you're thinking - if you want fast, simply buy fast out-of-the-box and enjoy it.