The tech REALLY THINKS it is the fuel head?, the one that runs between 500 and now 1500?
And the car only stumbles at IDLE, and after 10 mph drives well?
Buddy, time for a second opinion. If the problem is ONLY at low RPM's (idle) I do not think now 1500, on top of 105 to change the sparkplugs is a solution.
We have not even looked at wires, distributor cap and rotor yet.
Fuel filter, air filter when were they changed?
Good point about the motor mounts.
I always go for the cheap fixes first. Clean the ICV, see what happens, clean throttle body, see what happens, change sparkplugs, see what happens, remove dist. cap and rotor-inspect and clean-replace if necessary, see what happens,... and so on.
I get scared when a mechanic tells me:

"I THINK the problem is this..., it is going to cost $$$$$$ to replace it" ....(and let's see what happens)

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
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