I’ve been tinkering with our new 90 Mini and it is still running poorly at idle and low RPM. The previous owner installed a Weber 45DCOE and an intake. Seems like a lot of carb for the car. Any thoughts on this setup?

I think I am going to grab an overhaul kit for the carb to eliminate doubt about it being sound.

 

That's a bit big for a road-going 998, although it's been done & does work.
You might check the jet sizes & see if they are close to correct for a 998.
This should help:

http://www.s262612653.websitehome.co...ews/webers.htm

 

Far far to big on a std 998 HIF38 should suite better

 

The 45 is going to be too big in general for a 998. and if you can get it to work, it's a WOT carb anyway and you'll get horrible driveability from it in regular traffic and road use.

I've used a HIF6 (1-3/4") SU carb on a 998 and despite what people have said ("It'll never work") it works just fine because of the variable venturi effect of the dashpot. I'm not sure it NEEDS that big of a carb, but this is a track car that sometimes sees autocross use. Throttle response is still awesome as is low speed drivability.

That said, a 45 DCOE is a single orifice size that you can change via chokes and trumpets and whatnot so it will be a lot more particular and difficult to get it to run right. Certainly do-able, but likely not worth the cost/effort to dial in.

998 minis can run just grand on a single 1-1/4 carb but they do seem to top out on the fwy a little sooner than, say, a 1-1/2" carb will.

Best advice: find a cheap 1-1/2" SU carb and intake manifold. AAU or AAM needle if you have modified (1-7/8") exhaust and K&N filter.