Well,
I can proudly announce:
I'm the first owner with custom exhaust on Opel GT from my country and first happy romanian solo customer.My mod was Free Flow Catalytic Converter (catless downpipe) and Mach System with quad tips.
Even took more time than expected,
everything went smooth with 0 (zero) problems. 100% bolt on, I even had a bet with a friend of mine which said is impossible everything will fit and work perfectly, no re-dos, everything straight to the bulls eye.

to Solo people.
I have added only one special sealer for exhaust on the clamps as a matter of precaution everything else was in the package.
Because of catless downpipe I was afraid of CEL, but nooo, from the first run no cel, test it about 2 hours drive and NOTHING wet wrong other than my car trying to go sideways when I was WOT and ESC OFF.

When I took her for a spin my DIC was showing strong 25psi instead of 22-23psi before. I will test more.
I wanted maximum power and at quiet as possible that's why I went for this setup, I can't say it is quiet under heavy push but I can say is almost like the stock one under 3500-4000 rpm, it has a "quality" sound and pretty base, I love the rumbles on deceleration and some bangs from time to time which I think are because of catless downpipe.
For me this product is a jewel for my car

Here are some pictures:
Solo Mach vs stock exhaust
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Solo Mach muffler vs the huge stock muffler
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Solo Mach mounted on my Opel GT
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Sorry I didn't made pictures with the downpipe

but believe me that piece really looks like a piece of art
Solo Performance people: Steve, Jeff, Michelle and the others which I didn't interact with

keep up the good work, we, kappa owners need people and products like yours.