IML: 1990 imp

hi all im new to the club i just purchased a '90 imp (3/90) in near perfect condition from an old farmer it has all the bells and whistles and mark cross on it first question just curios the web site says that the mark cross option wasnt available until 91 mine also has factory steel rims with the wire caps and your website says this year only came with alloy? any way like i said the car is in near mint so the smallest problems are noticeable im waiting on parts for the air ride suspension but the only other problem is i took it to an automated car wash and during it the wipers started going and havent shutoff since i had to unplug the wiper fuse also the cruise stopped working and the engine seems to run a little ruff all this started at the wash the running ruff only shows in the gas mileage on the little pc in the car before i was getting about 18mpg now its about 15 mpg there is a click when the wipers come on and it appears to be coming from the computer box in the side panel under the glove box any clues ? oh and on the 3.3 cheap easy fixes for better fuel economy i.e. performance air filtration let me know. 1 last question the sticker in the drivers side rear window is that the production number? if so mine is 968