Pilot on a post maintenance test flight flying CE-550 aircraft reported throttle and flap control malfunction inflight.

Narrative

I encountered several issues during the test flight of Aircraft X on Friday. Here's a detailed account:After loading 220 gallons of fuel; I observed an imbalance of 300 lbs. in the fuel tanks (left: 800 lbs.; right: 1;100 lbs.). I balanced the fuel load while on the ground by cross-feeding. All systems appeared to check out fine.During the departure roll; nothing unusual was noted. However; during climb; I noticed a heaviness in the left wing. Upon reaching 3;000 MSL; I leveled off initially at around 2;700 MSL; with a slow rate of climb by 2;800 MSL. I corrected the left roll by adding aileron trim just after raising the flaps from the takeoff position to flaps up. The retraction of flaps caused the right throttle lever to be pulled forward; exacerbating the left-turning tendency.While in IMC conditions; attempting to diagnose the issue and questioning the ADI; I cross-checked with the right ADI; DGs; and magnetic compass. After confirming no rolling; I noticed the right-hand throttle was forward and the aircraft was climbing. I promptly corrected altitude and reduced the right-hand throttle.During landing back at ZZZ; on the RNAV GPS XX approach with autopilot off; another throttle issue arose. At glide slope intercept; with gear down and speed reduced to 160 knots; I selected flaps to the landing position. As the flaps extended to full; the right-hand throttle was inadvertently pulled to idle; causing the aircraft to pitch down. I regained control after the flaps were fully extended. A small piece; resembling white plastic; ejected from the throttle quadrant during this incident.Landing was completed without further issue. However; an unsafe gear warning occurred after retracting the gear from the ILS low pass. The gear was left down on the return to ZZZ.Post-flight investigation revealed that the flap indicator which moves with the flap extension and retraction was bent such that it was entangled with the right-hand throttle.Due to throttle movement issues; I recommend grounding the aircraft until the throttle quadrant is examined.