Volkswagen Repair: engine problem/exhaust problem, vacuum hoses, vacuum leak

Question
Hello,
I have a 1998 Volkswagen Golf with about 98,000 miles, at least 10,000 of which were highway miles from two separate road trips. I'm having a few problems, one of which I'm having trouble diagnosing.

It seems when the car isn't driven for a few days, it starts really, really rough. Sputtering, shaking for a few, then it seems to clear up. Also, if I let the car idle (warming it up or even stopped for a few minutes at a railway crossing) the car stalls. It takes a while to restart it and when it does, it runs really rough and sputters. The only other  symptom I've noticed is a reduction in gas mileage. I used to get about 340 miles on a full tank, and now I'm straining to get 310. The dealership told me it would be $70 just to look at the problem.

Another question I have concerns the exhaust system. This has been going for a while and I've done some minor repairs myself to shore it up. The dealer and an independent repair shop told me it would cost $1,800 to replace the exhaust system -- that's the downpipe from the engine to the catalytic converter (the first part that went bad, btw -- a $500 part), two mufflers, the catalytic converter, pipes and fixtures. Is there another option?

Any advice you could provide on either subject area would be greatly appreciated.  

Answer
One at a time ...first the running thing...where I would look first is that it sounds like you have a vacuum leak somewhere - the car is getting more air than fuel(stuttering) -the poor fuel mileage is due to the fact that your foot is farther down on the pedal than would normally be (more gas) because of this.  Solution I would first try...get a spraycan of of brakeshoe cleaner(basically an alcohol product).  It sprays a direct stream.  What you want to do is get your car running and idling and then spray all the intake connections at the gaskets, around the   ends of tubing that are suppose to be clamped tight, the ends of vacuum hoses, in the plug holes a bit while the engine is running around the head gasket, the bends of the vacuum lines or bends of rubber hoses.  What you are trying to find is a sucking leak and with the engine running the idle will change either race up or the car will die.  This spray will not hurt your vacuum hoses or other rubbers, or the engine--more of an octane booster.  If you wanna see give the intake a shot and you'll hear.  Once you do find the leak and I am sure you will, that is where you gotta fix with either a new gasket or vacuum line or whatever.  My first guess as rubber parts don't last forever.The dealer says $70 bucks tells me they will find it within the 1/2 hour.

Exhaust...ouch...my option : first check the yellow pages for jobber part shops that have VW such as BOWWOW auto parts or NAPA Auto Parts to see the cost there...napa is gonna be higher than Bowwow however they both should be lower than the dealer.   
    Another option, and I have used it many times...local autowreckers..you can either call them to find out who carries your car parts that would fit your year or they will let you remove them yourself  charging X dollars for exhaust parts, Y dollars for suspension, etc.  Such is the case here with Pick your Part.  They can tell you what years fit what but they don't have knowledge of  what is in the yard you gotta do the foot work and wrench work yourself.  Check around maybe there is a VW speciality wrecker(mind you I think he would be somewhat pricier but he would probably have taken the parts off himself so people don't get those pocketable extra's which is good coin.  Looking there can't hurt, besides these cars got into accidents maybe with new altenators, shocks, seats, paint jobs, etc.  Accidents don't choose which car to hit.


Another site to check out with more VW nuts is VWVORTEX.com.  Maybe they can also help with your starting if I am wrong. There is also requests for parts there.
That's all I can tell yer mate. LOL

Sorry fer the ramblin on and on.