After market pipes

I am currently looking to buy a used M800 and have noticed that several are advertised as having after market exhaust pipe upgrades,I am a little wary of these as I believe the stock pipes are better suited to the engine regarding length and compression and therefore changing the pipes can have a detrimental affect to engine ferformance and MPG.What are your views on this or am I being a little paranoid

Can't answer for the later, FI bikes, but mine came with Highway Hawk straights.  They'd not been set up properly & I ended up removing the PARE valve to stop excessive backfire.  They were way too long for my liking so I had about 18" lopped off the end - which looked the dogz, but made 'em way too loud so I then had to have a pair of end-cans made up.  I also had the bike dyno-tested which sorted out all the running issues (stutter on acceleration)

Now they're set up, it runs fantastic & sounds great.  MPG wise, I'm getting about 37 ish, but I ride on the "progressive" side of steady.  I know other members get better economy than I do.  If my bike had come with originals, I'd have changed them straight away - the OEMs are (IMO) pig-ugly.    If that's the only thing putting you off an otherwise ideal bike, I wouldn't be put off - they may need setting up though - you could always live with it till an original set come up on ebay - there's two sets on there at the minute

hi patch. lots of people change their exhaust  I had brand new 55 plate m800  and put highway hawk snake pipes on it( google it you probably find a pic of me with the exhaust) never had an issue in seven years and bike run better slightly better acceleration  reved more freely... sounded awesome..                    just put highway hawk short cuts on my new m800 bike responds much better goes like a bat out of hell now ,,, whheeeee.   no issues no backfire   and the weight of the standard exhausts are heavy  so taking loads of unwanted weight off the bike too.   just check to see what has been done as some exhaust require a power commander if air filter mods have been done.. a simple test ride will show up any exhaust issues immediately... ride safe   Magic

I've ridden the Intruder now with stock, debaffled stock, gutted stock and aftemarket pipes. The aftermarkets had the edge sound wise but the stock pipes suit the bike best visually IMO. Gutted stock pipes give you the best of both worlds possibly. Debaffled pipes (just the backplate and baffle tube removed) give a pleasant burble. Not everyone likes loud pipes but if you meet other cruiser riders regularly, the stock pipes will probably sound too quiet after a short time owning the bike. There's a wealth of advice and how-to info on this forum regarding pipes. As long as you don't change the air filter as well, the bike will be fine with 'open' pipes particularly with fuel injection as the ECU will make adjustments automatically. If I had the choice of an 800 with aftermarkets and I liked the sound on the test ride, I'd buy it. You can't always predict liking pipes if you just buy them.