The 4 rubber pipes are for idle air delivery. Idle air is routed past the injector nozzle tips so that the small volume of idle air pulls the entire fuel charge into the cylinder. AFIK, all of the CIS cars do this in some fashion or another. After opening the throttle, the amount of air flowing through the idle air circuit is negligable.

As far as sluggish performance there could be multiple causes. The first thing that comes to mind is poor injectors. If they are pissing and not spraying at low flows it really hurts performance, most noticeable off the line. Late cam timing from a stretched chain could also be a culprit, as well as tight valve clearances. Of course it's all just speculation without testing whats actually going on.

Keep in mind that this engine was designed to make power in the upper revs, and will never be a torque monster off the line.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff