Andrei hi and welcome
Nice looking 33 you've got there
I've got the same BORBET wheels on my Sud, but I'm missing the center caps ! Got any spares ?
Regarding your engine/vacuum/catalyst/lamda sensor issues :
Personally, I would get rid of this stuff !
First of all you need to find a Motronic ECU out of a non catalytic version 33 16v.
Then you will need an air flow meter from the same type of engine, the wiring loom, the top intake plenum with the idle valve
, the throttle position SWITCH, rather than the throttle position sensor that you have now on your throttle bodies, a bosch dizzy and an oil pump from a 16v engine that has a dizzy.
All these parts are interchangable from a non catalytic 16v 33.
Why go into all this trouble ?
Change this stuff and make your car work without needing a catalyst, chop off the catalyst from your exhaust system and get rid of the vacuum system ( apart from the vacuum of the throttle bodies ).
Then, go for a drive
You will find out that you will no longer have the problems that you do now, and you will also discover that you will gain a lot more power ( although in papers its supposed to be only 5bhp difference ), better throttle response and torque
Been there, done that, felt like I was driving a totally different car and couldnt beleive the difference in power - especially after 4000 rpm