My vehicle is converted to Toyota Sienna 1999 engine from Ford freestyle 2005.

Problems:
*It was unable to climb hills and runs very heavy. *Guzzles fuel.
*Jerks when accelerating

NOW:
1. I have fixed gear issue.
2. Done servicing as directed by the mechanics.
(Changed plugs, Nozzles, injector, mad, changed plugs coils).
3. I cleaned and welded exhaust/silencer.

OBSERVATIONS
*The vehicle works well as soon as mechanics is done fixing it, but next same very issues reoccur.
*Fuel smells inside the car at startup.
*The computer readings are incorrect e.g fuel data error (there is plenty of fuel), oil level 0% (atf and engine oil intact), no coolant (coolant intact).
*Hard starting atimes.

I was told to service brainbox. Now I ask, is that the true solution? Please someone help.