wires and box attached to throttle peddle

[srnehoda]

hope some one can help
I have been tuning up my 2003 club car gas precedent golf cart
I replaced fuel pump, carb,spark plug,old gas
it running better but when I went to adjust the linkage to throttle peddle I came across a black box 12/03/03 g002121 which is connected to the gas peddle
it got orange green white black and red wires going in to it and seems to some how electrically control the speed the cable hardly moves the carb.
The problem is at low speed can't seem to get slow steady speed without more peddle if i floor it it goes good up to rpm limiter 4000 rpm and kills it till back in rpm range.
my question is what is the black box with the wires and is this the problem

club car gas PR0327-297460
stock engine