300 E Hesitation with A/C on

I've been browsing this forum and applying useful advice from it for 2 years running, but this is my first post. I must say that this is the best collection of MB technical advice I've come accross and I read the forum everyday.

Here's my problem:
My 1988 300E hesitates on acceleration from stop when the A/C is on. It doesn't do so with the A/C off. I recently changed the injectors, distributor, plug wires to resolve a rough idle problem but this did not solve the hesitation issue. It has 150,000 miles on it and drives like almost new except for this prob.

Anybody have any suggestions/solutions. Thanks in advance