I had the same problem with my mom's 88 TE -- rough idle, stalling when coming to an abrupt stop, and serious throttle lag -- step on the gas and nothing happens.
I replaced all the rubber vacuum line ends, including all the lines to the computer and to the tranny. This helped, but didn't solve the problem.
I then checked the idle control valve (in front of the fuel distributor under the air cleaner). The hoses were rock hard and rattling around on the nipples. One also holds the cold start valve, and that was loose too.
I replaced them, big pain in the rear, but the throttle lag dissapeared and most of the roughness at idle, although I still have a lean running condition I've not gotten around to fixing.
Check all the rubber hoses that hold vac, and I suspect you need to replace the idle control valve hoses.
Also, see the posts about checking the O2 sensor -- if it is bad, all sorts of strange things can happen.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!