I have a stock 72 GT, now after reading through a lot of threads I'm not sure I made the right decision. I wanted to try to plan ahead for when the time comes to rebuild and probably go to the 2 liter from the stock 1.9. I see what apears to be the rule of thumb on most posts going to a 2" then 2 1/2" over the rear axle with a couple of resinstor tips for sound & appearance etc.. I can't afford to go with the header let alone the new 2" 0.D. Stainless exhaust Gil has that bolts on to the stock manifold (very tempting though). So I went the custom route and told the guy at the shop to give me 2 quotes, A) replace the existing muffler (stock exhaust) and add on the OEM resonator I just picked up used in pretty good condition. B) go 2" from the manifold back to the 2 1/2" over the axle etc. having stars in my eyes and a bit of Opelitice I was willing to part with the resonator if it made enough sense. This guy seemed pretty knowledgeable. I think what was an oversight by me is that in visiting the wealth of knowledge within this wonderful website I saw Very few who has the low compression stock 1.9 CIH looking to modify the exhaust. On top of that most people have installed headers and done so many engine mods that made things more difficult for me. All that being said the recommendation I got sounded like a good compromise for what I was picturing as moving up in the world jetting out my 32/36 DGV utilizing the larger exhaust etc.and being a layman I turned to the guy that had been doing exhaust work for 30 years and the other eye on my wallet, after listening to me run down the two options I think he tried to give me the best of both worlds. He suggested cutting in with the 2" after the wye where the 2 head pipes merge into one. I questioned him on that because it seemed to defeat the point of going up to the 2", he said it wouldn't make any noticeable difference. He also suggested going 2" all the way and using the stock resonator. I'd mentioned wanting the 2 1/2" up & over the rear axle etc. again he said it would be negligible with my application. So I slept on it and called Todd which is where I purchased the resonator. He said for my car 2" was too big and it would labor climbing up the RPM's slowly due to insufficient back pressure. I know Todd has been around the Opels for years and anyone who has played around with that many Opels was worthy of listening to, besides I had cold feet with the wye & resonator thing. I took my car in the next day and explained to him the conversation I'd had to go to the 1.75" and was changing my mind. He talked me back into the 2", I trusted him to execute the job, thinking he'd had enough information based on my concerns. He did a great job BTW, installed the bung for the air fuel ratio guage perfectly. The exhaust is tucked up neatly close to the chassis, using a round 2" muffler going 2" up & over the axle, the resonator placed perfectly. No excessive movement like the old exhaust but enough so it moves when the engine & tranny bob up & down. That's why I'm in peril right now. He really does do good work. He said I'd get enough back feed from the resonator (something didn't sound quite right with that) so off I drove. Todd was right though, I have DEFINITELY lost my low RPM torque, she barks like a dog down there, it does show more potential between 3000-5000 RPMS. I have yet to jet the carburetor well enough to get up to 6-7k or better. After reading more on the subject I see the elaborate sports cars use a smaller exhaust for the low RPM range and open up to a larger exhaust after the RPMs have climbed high enough to meet the demand. Even though that's not realistic for the Opel (for me) it got me thinking 1.75" from the wye to the muffler? Would leaving the 2" muffler in with the 1.75"head pipe defeat the purpose? Leave the 2" up & over the rear axle to reduce friction loss there Still sounds like a good idea? Keeping the resonator for sound & looks? Go with the 2" "U" and a couple of resonator tips? Keep it all at 1.75" to the resonator (my least favorite)? Can anyone weigh in and give me there opinion? Should I be patient and put up with the low end bogging while I have the low compression 1.9 and jet away to get some upper RPM improvements ? Remove the baffles in the OEM resonator to open it up more? Frankly guys I'm a little confused I'll take some pics, that makes any feedback a lot easier. I will probably never get more than 110-120 HP from a 2 liter and possibly a 38/38 Weber anyway right? Iv'e been driving this car since I baught it in 87' for street use only so maybe the 2" to 2.5" exhaust is more than I'd want if I'm watching the gas mileage and trying to get my RPMS to 6-7k once in a while just for kicks. I wanted to detail the story and I wanted to post it in case anyone else (there always is) can learn more from reading this if they are looking at an exhaust modification and see how instrumental it can be in getting what he or she may be looking for as the case may be. Thank you in advance for any feedback which I'm certainly open to. I'll try to get the pics up in the next few days.