Let rationalize this post for a moment. From what I read there were 2 things wrong with the car (a high mileage, 6 year old car at that). A finicky top and a MAF/O2 sensor issue. The first should have be fixable by a competent shop with knowledge of the top mechanism and the updates since '99. The second was the failure of 2 components that are common to ALL EFI equipped cars and fail at a similar rate regardless of make (yes, your Lexus will be just as vulnerable). The idle issue sounds like the result of a botched EFI diagnosis IMHO. There's probably another sensor that either caused the MAF error, was masked by the MAF error or the MAF / O2 sensor installation was botched, just like the "top fix".
ALL of the other issues and money spent were the result of customizing, i.e. self induced. :ah:
Enjoy the Lexus, it sounds like you're better suited to that level of performance and style.
I've owned 9 Porsches in my lifetime from my original 914 2.0 through my '89 930 and now my Boxster S. Each one of them had a unique charactor. Every one of them had it's quirks but ALL of them put a smile on my face that no other car I've owned (20+) could ever come close to.