this could be lack of power due to a clogging muffler or cat converter.

also is very important that the fuel return lines>I believe there are 2 for each bank.are connected properly. there are 3 hoses coming out of the fuel regulator. the misc.hoses are just as important> they are for vacuum which opens the waste-gates if they are open then I believe this is the problem. Now these vacuum hoses have restrictors inside and they must be replaced at their designed junction> they are different sizes. If you look up a motor manual these items are discussed in the engine rebuild section. The engine is somewhat on the heavy duty side! But, be sure the H2o pump and Electric fans are working. Lastly it easy as 123 to mess this car's electrical!! yes it will run,,,, but poorly. if eveything is normal and functional "you should hear" @ passenger side in engine bay @ strut housing a" click click pop" that the electrical pop-off for the turbos not allowing them to build complete pressure on the waste-gates. I believe the turbos waste-gates are closed & the the engine combustion cycle is maxed out & cannot get a second breath. Good Luck! The Cats are heavy duty and the smog pump generally filtered any thing out due to the extra rail feed into the exhaust manifold and was burnt before the cats!! Contact MIC for all Maserati Biturbo info and parts. Maserati International Club. Seattle, Washington