Ihave a 98 626 and it shakes a lot in all gears. So i raised the idle so it shakes less in park and nuetral now. the rpmfalls to around 5 and starts shakind.Under the hood i can hear a hissing noise and it sounds just like the vacuum line becasue i pulled one of the hoses and the sound was the same. The sound seems to be coming from around or under the intake manifold. Any idea's on what the problem can be.. a vacume diagram would be apprieted. The problem also started after i got my tranny gasket changed, so im think it might be a hose that he forgot to put back in. The car shakes in only when the gas is not pressed and when the brake is press it gets a little worse. Also my belt sqeeks but i had a replaced last year.
(ps i installed new spark plugs, sprak wires, air filter, fuel filter, pvc valve, MAF,cleaned theT.B with carb cleaner,and addedfuel cleanera fewtimes.)