If you only want a few hp like that then that is a lot of effort for the gain. I would say you could probably do that with a custom exhaust and fuel and timing and maybe CAM timing. Or near it. The engine and fuel system will support that now. These run pretty lean once warmed up and something as simple as lying about the clt temp to get it in cold fuel and timing makes a big difference. Maybe higher compression pistons which there are stock ones if you do not already have the 10:1 ones.

I found this on another site:

I'm working on scant details and a lot of assumptions about the M103 AMG motors. The idea is, now I've got a used M103.983 into the W201 with the 22/62 cam in, I'm looking at rebuilding next. Most importantly rebuilt head/valve gear for longevity but I'd like to at least have new rings/bearings in the bottom end, want to chase another 30hp or so (headwork, comp shave, fabbed headers), but all over the labour expense and size of the job means I may as well throw in other parts for as close-to AMG spec as I can get the 983, even a couple of grand for pistons is okay by me since the whole thing is going to cost thousands anyway from what my experience has been thus far, so I'd rather just throw the whole wallet at it and get the final results that I actually want the first time out. Not 2 grand here, 2 grand there and it winds up costing more in the long run going piecemeal for the results I'm going to chase either way.

I want like 250bhp in this 201/M103, more really. I'll put a 30/70 in and swap to a manual if I have to, but I want the power, n/a, no turbos, no more engine conversions, the motor should have it if I can get that power from an old Holden 202. This motor is much more n/a hp potential than a bloody 202.

So the AMG M103 motors. I've seen some specs for a 3.0 litre version and 3.2 litre version, basically they look like stock 98x motors with 10:1 compression and a cam, I'm guessing a 0.5-1mm head shave will get the compression, I've already got a roughly-AMG spec cam in, should be good for 215PS in the 3.0 and 230PS with the oversize pistons of the 3.2 build.
But I think those are mid-80s AMG builds for the 124, the AMG 3.2 in the W201 didn't appear until 91-3 from what I've heard and had more like 250PS. There's a guy on 190rev who posted about his, england based iirc, has 250PS all plated and everything (and it was either his or another stock one I read about that actually returned 255 on an engine brake in practise).

I found this picture that makes me think AMG used the factory exhaust manifold.

AMG M103 by ttownthomas, on Flickr

and I have read this from yet another site.

"AMG’s package for the M103 opened the 3.0L SOHC inline-six up to 3.2L. The modifications included an overbore, longer stroke, and more aggressive cam with solid lifters. These modifications gave the car a substantial increase in power, up from 188 horsepower in a non-catalyzed M103 to a full 230 horsepower."

Also read this:

"if memory serves, the
early AMG 3.2 is a M103, bored & stroked to 3.2 liters."

Also found this:

M103 3.0 to 3.6 Build Discussion

Have a look at the site 190rev com , some have swapped in a M104 where the car had a M103

Other than details, a M103 to M 104 3.0 24 V swap is more or less = to swapping from M103 to M104 3.2 except for the FI system.

Do some parts pricing for the M104 3.0 24V CIS system. Look at injectors / fuel distributor / EHA control valve / throttle position sensor. Also price out a distributor cap / rotor and EZL module ( Ignition module )

My 97 SL320 M 104 with Bosch ME 2.0 / 2.1 electronic FI is rated at 228 HP @ 5,600 / 232 Ft Lb @ RPM 3,750. The 97 E320 with the same engine is slightly less, near as I can tell it is due to smaller exhaust.

For a 97 SL320 the net tells me 0 to 60 mph 7.8 seconds Quarter mile 16.5 s @ 91 mph . I know the car weights about 4,100 LB

No they didn't.

No it doesn't.

Both are 48mm.

It's the base block. The 2.6 block doesn't have steam cuts between the cylinder bores, but is otherwise the same as the 3.0L M103.

Or the 3.0L OM603

Because they bored it.

No idea on those.

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1993 190E 2.6 Sportline