1996 Impala RS Serious Problems

I need some insight on this strange issue I have encountered. I went to do a mobile install on a 1996 impala ss. the alarm was a clif 3.5 with remote start. I installed the alarm and everything went great. The customer drove the car 3 blocks then it shut off on him and would not restart this has been partially solved by changing the fuel pump relay and pump (the relay looked fired on its contacts). the car now starts and idles but dies with any load.  Also the car started haveing other wierd electrical issues: the door locks sometimes work, sometimes the drivers door lock gets stuck locked as if you are holding the power lock button down. the odometer sometimes works, the fuel gauge is stuck on full, the trunk release seems to now be tied in with the hazard lights.

I have been doing installs for years and the biggest mistake ever made led to a blown fuse. i have done many of these caprices and impalas with no problems, certainly never had any problem like this. I am inclined to say that none of these issues are related to the alarm/ RS, but since they all showed up right after I did the work, I will not leave the customer hanging if there is a chance of it being my fault.

I have since removed all the alarm components so the car is all stock. all the above problems are still happening.

anyone have any ideas what could be causing all these problems?

anyone feel that these problems could be caused by installing a simple RS alarm?

thanks for all your help

you are going to think i am nuts but check the ground wire in the trunk on the left hand side that in near the trunk spring. I had the same problem and it took me a week to figure that the ground was loose.

Checked grounds: they all look good nice and tight

used t taps, they only bit the wires i needed. nothing by accident., never probed anything with a meter, actually never had to tap anything except tach, acc, and brake wires because there ahd been a basic alarm in there before