91mcb300e

Okay, I've been thru a ton of forums but I think it's time for some specific advise. I bought a 91 mb 300e 3 weeks ago. The car did not start at all, so I had it towed to a shop. After checking, the shop changed the battery and it started up just fine so they asked me to pick up the car. Picked it up later that day and it drove 1/4 mile down the road and idled fine but when I hit the gas it sputtered out. Was able to push start the car and drive it back to the shop. It stayed over night and the next day the mechanic said it started right up and they couldn't duplicate the issue so they asked for me to pick it up. When I did, the car started right up and ran perfect for a week. So I installed an aftermarket deck, amp and sub according to oem standard, and hooked the amp power cable to the positive connection on the battery (like I always do) after tuning the system the car wouldn't turn over and hasn't since. I thought I deep cycled the battery so I took it to auto zone and got it charged. I un installed the system and Just in case I gave the car a tune up (plugs, wires, dist. Cap, rotor) everything locked tight and in the right order. Still won't run. Thought it was a fuel relared issue, so i took the air filter off and checked the fuel pressure line and there was definitley fuel coming out so i changed the fuel filter, no luck, changed the MAS relay because both fuel pumps weren't engaging when I turned the key to position 2, still no luck...was told the OVP could be bad even without a blown fuse, so I'm replacing that next because the car turns over for a second when I introduce starter fluid to the system. Aside of a new OVP, and hopefully not but possibly new fuel pumps...does anyone have any advise ???