Nomad400E

Hello, I have a 92 400E with 172K miles. The engine started missing on accl, so I took it to the dealer & they told me the dist. rotor had corrosion & they replaced one & cleaned the other & also cleaned the dist. caps. They also told me it might need plugs & wires. $300 later, it ran no better so I bought new Bosch wires, plugs, caps & rotors on line & installed them. It starts easy, sounds good but the performance is not there. From a dead stop, at about 4500rpm it hangs up & starts missing, does not upshift. If I let off, it will upshift and you feel each upshift. It cruses fine, but under load if you try to accl, it is very slow . Any suggestions? thanks!!