stumped

Hi all, im new to forum and was hoping to get some advice.I bought a 1987 eighty eight from my father and when he had it he was having problems with it stallin while in drive at a stop.He has had it to 3 garages to try and have this problem fixed but it still happens and there is a thump in the transmission every so often when its changing gears.The following is what has been done(brand new parts) fuel filter, fuel pump,plugs,wires,crank sensor,idle sensor.Also the modulator was replaced but with an old one that he had.Any help with this would be appreciated.

TPS or MAF been touched?

As far as i know they haven't been but i am going to have them checked and get back to you.Thanks for reply.