'96 Jetta - acting up like C R a Z Y - weird problem...?

Let me start by giving you some details on the car and what I have done (recently)

1996 Jetta GL

2.0L Engine

5 Speed Transmission

I parked this car a couple days ago and it ran perfectly. All I did was leave it

sit for 3 days or so while I tracked down and changed some bushings on the

lower control arm.

The thread-housing was stripped out on the bolt at the pivot bushing so I cut

an access through the subframe and then this morning drove it 1 mile to the

shop (where it seemed to run fine) and had a weld done.

I had them weld the flange of the head of the bolt to the subframe and also in the

back where I cut him an access and had 1/8 inch steel plate (1 inch X 1 inch) welded

over the access.

That's it.

Now, when I left, I didn't get even a mile down the street and my car FLIPPED OUT

on me.

The car will idle fine, but when driving the check engine light starts flashing like crazy

and the car dies, the rpm's go absolutely insane, jumping around on the dash, but seemingly

NOT on the motor.

Takes it s e v e r a l times to start back up when it does this, seems to be especially when I press

the brakes.

I don't understand since it ran fine before.

NOTE: The check engine light has always been on for a cam sensor, but the timing

IS correct (set it myself) and it's a faulty sensor.

The car has always ran perfectly and I don't understand.

The last car I had sitting where this one sat for the last few days got set on fire

by someone (yes I know set, because it had no motor or battery...) and I "think"

that the gas cap had been messed with on this one.

What problem is this?

Could it be caused by someone adding a "special ingredient" to my tank?

Help me please, I love my Jetta...