I have been through this thing enough;
1984 TD 150K miles

new timing chain
comp check (all over 300)
valve adjust
clean tank out of algae (BTW don't bother with algae purge it is not a long term solution best to pull tank)
replace injection gaskets/washers
check injectors (have 2 rebuilt) car runs worse after
change primary fuel filter about 20X thanks to algae problem
change 2ndary 1X
have local dealer set timing (wow can they overcharge)
clean banjo bolt
run standyne fuel system cleaner through several times

all of this finally fixed my loping problem, but now the car seems to have very poor power (less than before I started all this) and gets about 20mpg....any ideas at all what the problem might be?
I have just about had enough of this thing and would like to sell it...but sure would be nice to get it to run right first
if anyone knows a shop that can work on this thing in or near Buffalo NY please help.....I am now willing to pay.

also...any chance I might have a bad IP???

Here's something to consider. Someone might have over tightened the rack damper pin to get the idle to stabilize. If your rack damper pin is silver colored, get a new gold colored one (~$30 from FastLane?) and set it properly (procedure in the archives).

Sixto
91 300SE
87 300SDL
83 300SD

would the rack dampner have an effect on fuel economy?

I'm not sure. What I've read in the archives regarding installing a new rack damper pin is that if you set it too tight you lose power.

Sixto
91 300SE
87 300SDL
83 300SD