Hey Damico,
Why did you replace your alternator? It would have no effect on the hesitation. Either it doesn't work and your battery goes dead or it works, (excluding other things such as noises, etc.) As far as the shifting into N and having the RPM's increase - of course it will as all of a sudden there is no load on the engine. Do you really trust this mechanic?

My 88 TE also had a hesitation and it was completely cured by changing out the rotor, cap and wire to the cap from the coil. All were in bad shape (from previous owner.)

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'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles