You could have some carbon buildup on your intake valves. While not as effective as cleaning from the intake side, a can of BG 44k fuel system cleaner put into 1/2 a tank or less will help. If you don't have this product available near you, Chevron's Techron product is a good alternative - and it's available at all automotive stores and Chevron stations.

Of course - deposits could have nothing to do with your problem, but I always like to try the quick and easy solutions and move on to the more costly solutions as a last resort.

Troy
1995 E420 75k