can a brainbox.be de cause,of a vw t4 bus.formally it does nt raise$do slow.now after so much repair.it work,bt not fine.if it move 4like 10mns,it stop.if start,it will move a while$stop again.bt my mechanic$rewire say,i shld convert it to carburator.and i dnt knw,if dat is de solution.pls anyone wth similar experience,shuld help me out.

Your initial problem could have been fixed with a simple scan.

Could have been a vacuum leak or dirty throttle body usual cause of idle problems.

Now only GOD knows what they have(mechanics don't).

The advise they gave is no better than tying a Camel to the front of your bus

Have them tell you everything they have done and post them here, maybe Siena can reverse engineer their work.

You'll need to start fresh with a new mechanic.